THOMAS YOUNG, QUAKER SCIENTIST

by

GENEVIEVE MATHIESON

Submitted in partial fulfillment of the requirements For the degree of Master of Arts

Thesis Advisor: Dr. Gillian Weiss

Department of History

CASE WESTERN RESERVE UNIVERSITY

January, 2008 CASE WESTERN RESERVE UNIVERSITY

SCHOOL OF GRADUATE STUDIES

We hereby approve the thesis/dissertation of

______

candidate for the ______degree *.

(signed)______(chair of the committee)

______

______

______

______

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(date) ______

*We also certify that written approval has been obtained for any proprietary material contained therein. ii

Table of Contents

Acknowledgements...... iii Abstract...... iv I. Introduction ...... 1 II. The Life and Work of Thomas Young...... 3 Childhood and Education as a Quaker...... 3 Medical School and Young’s First Publication ...... 7 Quakers and University...... 9 Pursuing a Medical Career...... 11 Disownment ...... 13 Early Optical Experiments...... 16 The Royal Institution & Maturation of Young’s Optical Theories...... 21 Leaving the Royal Institution...... 27 Conflict with The Edinburgh Review...... 28 Medical Practice and Egyptology ...... 31 Revisiting Optics...... 34 Young as Bureaucrat...... 37 Young’s Later Life...... 41 III. Conclusions...... 43 Impediments to Young’s Optical Theories...... 43 The Mathematical and Scientific Styles of the English and the French ...... 48 Quaker Science and Quaker Schooling...... 50 Quakers in the Royal Society...... 53 Young As Quaker Scientist...... 56 Bibliography ...... 60

iii

Acknowledgements

Firstly, I would like to thank the members of my committee for working with me during this endeavor. I am particularly grateful to Gillian Weiss and Alan Rocke for their involvement from the beginning. Without their support, suggestions, and assistance, this thesis would not exist.

I remain grateful to all of my friends and family for their ongoing encouragement of and interest in my academic progress as well as for providing reminders that there is life outside of school. I don’t have enough space to thank each of them individually, but I must offer particular thanks to my parents for their confidence in me, to Angie and Brent

Robinson for being enthusiastic early readers and to Mindy Miller for research assistance and cheerleading above and beyond the call of duty.

Finally, I would like to thank my husband Jim for providing countless meals and constant moral support, for being a willing reader of drafts and for his unfaltering belief in my ability to see this project through.

iv

Thomas Young, Quaker Scientist

Abstract

by

GENEVIEVE MATHIESON

Thomas Young was a widely accomplished polymath who discovered the principle of interference of light. This was just one of his achievements, made in the midst of practicing medicine, working as both a professional scientist and bureaucrat,

deciphering portions of the Rosetta stone, determining the causes of color vision, and

writing prolifically on all of these topics. The interference of light was later shown by

Fresnel to be conclusive proof that light was vibratory rather than corpuscular. Given

Young’s strong support for vibratory theory, this thesis seeks to determine why Young did not pursue his optical theories further. Through study of Young’s Quaker upbringing, an analysis of Quaker schooling and scientific practice, Young’s work and its reception by his scientific peers, I argue that Young’s scientific practice was inextricably linked with his Quaker background.

1

I. Introduction

Thomas Young was a polymath, a talented physician – though lacking in bedside manner – a natural philosopher, a linguist, and a bureaucrat. Throughout his life he varied roles so frequently, he could almost be charged with dilettantism. Nevertheless, Young’s accomplishments ranged widely. In physical optics, he discovered the principle of interference of light, explaining diffraction phenomena and supporting the vibratory or wave theory. In physiological optics, he was the first to suggest the existence of single-

color receptors in the eye and is credited with discovering the causes of color vision and

color blindness.1 He defined the modulus of elasticity (now labeled Young’s Modulus) as

the ability of a material to withstand length changes due to compression or extension. He

published a comprehensive treatise on consumptive diseases that was inspired by his own

experience with tuberculosis, and a survey course of medical lectures. Young attempted

to decipher the Rosetta Stone and was able to complete a version of the demotic text

before Champollion completed his own decipherment of the hieroglyphics. Young’s

industry was astounding; in addition to his scientific and linguistic research and

publications, he also maintained a career as a physician and bureaucrat.

Young was an ambitious man, but one who retained a strict adherence to honesty,

extended to the point of tactlessness. He refused to soften a harsh truth and tended to

assume that his audience was his intellectual equal, traits that explain both his failure as a

Royal Institution lecturer and his only modest success as a physician. Young was born a

Quaker, a Christian sect that rejected worldly goods and maintained a strict sense of

morality. His parents were of modest means, but his great-uncle Richard Brocklesby’s

1 Thomas Young, “The Bakerian Lecture: On the Theory of Light and Colors.” Philosophical Transactions 92 (1802): 21. The theory is now called the Young-Helmholtz trichromatic theory, and refers to the cones in the eye. 2

social status and his grandfather’s insistence on a classical education gave Young the

schooling and connections necessary to travel in rarified circles. His membership in the

Royal Society connected him politically, his profession as physician provided him considerable income, and both combined with his intelligence to yield countless

opportunities for research and publication.

Despite Young’s widespread achievements, however, he did not always take his

projects to completion. Although Young discovered the principle of interference of light and addressed a few interesting cases of diffraction, he demonstrated it only for two rays or sources of light and failed to apply it more widely to optics. As a proponent of the vibration or wave theory of light, Young also tried to use the principle of interference as proof of light’s vibratory nature. While Young lived to see his vibratory theory of light vindicated, he did not shift the paradigm himself. Given his brilliance and scientific ability, it is curious that Young himself was not able to take his discovery past simple demonstration and to its broadest application.

In this paper I contend that Thomas Young’s early religious background was influential in forming his personality and character, and subsequently his scientific style.

This paper, therefore, is an investigation of that relationship. By portraying Young’s life and work in a holistic fashion, I intend to demonstrate that Young’s scientific practice was inextricably linked to his Quaker upbringing. 3

II. The Life and Work of Thomas Young

Childhood and Education as a Quaker

Thomas Young was born in 1773 in Milverton, Somerset, to Sarah and Thomas

Young. He was the eldest of ten children but spent little time in the company of either his

parents or younger siblings; perhaps due to their rapidly increasing family, his parents

sent him to be raised by his aunt and maternal grandfather. Although Young’s father

worked as a mercer and a banker, his parents were not particularly wealthy. However, as

Quakers, they had access to a very strong social network that offered the younger

Thomas opportunities beyond his family’s apparent economic means.

The Quakers, or Religious Society of Friends, are a Christian Protestant sect, one of

many that formed in England during and after the English Civil War. Cromwell’s

Protectorship was a time of tolerance for religious dissent, and so some denominations were able to gain massive membership before the return of Stuart rule. The Quakers formed in the 1650s and grew swiftly through the evangelical efforts of George Fox, who served as a leader of the sect from the 1650s until his death in 1691. By 1680, there were an estimated 60,000 Quakers in England and Wales, though that number dropped to approximately 20,000 by 1800.2

During the eighteenth and nineteenth centuries, Quakers stood out in their speech

and dress, their refusal to tithe to the Anglican church and their refusal to treat any man

as anything other than an equal. They would not swear oaths, claiming instead that a

habit of truthfulness should absolve them of the need to swear oaths and that requiring an

oath was equivalent to questioning a Friend’s honesty. In addition to a reputation for

2 Elizabeth Isichei, Victorian Quakers (London: Oxford University Press, 1970), 112. 4

isolation and strangeness, Quakers were also reputed to be honest, forthright, and hard-

working.

Quakers called their displays of faith, such as donning plain dress, testimonies. Most famously, Quakers were strict pacifists. Eighteenth- and nineteenth-century Quakers could neither serve in the military nor celebrate or acknowledge military victories.

According to Robert Barclay’s Apology for the True Christian Divinity, war sprang from carnal lusts and was unchristian.3 Dedicated to the concept of equality among men, they

were also profoundly opposed to slavery. Protests against slavery and war took many

forms among Quakers; while a teenager, Thomas Young refused to consume sugar

because of its association with the slave trade.4

To ensure that their children learned the tenets of Quaker faith, the Quakers

established their own schools, outside the purview of Anglican church. They did so

despite the Act of Uniformity of 1662, passed by Parliament in a backlash against

Puritanism. In addition to requiring all ministers to publicly subscribe to the Anglican

faith and use The Book of Common Prayer, the Act forbade Dissenters to teach without a

Bishop’s License. This requirement effectively denied Dissenters the right to create their

own officially sanctioned schools. In true Dissenting spirit, however, Fox and his

contemporaries encouraged the founding of Quaker schools under the auspices of local

Meetings. Numerous unlicensed Quaker schoolmasters were cited or prosecuted for

teaching children to read and write. Contemporary ecclesiastical records list dozens of

3 Robert Barclay, An Apology for the True Christian Divinity (Philadelphia: Friends Book Store, 1908), 528-9. 4 George Peacock, The Life of Thomas Young, M.D., F.R.S. (London: John Murray, 1855), 16. Young was chastised for the practice by his uncle Brocklesby, who wrote “Your prudery about abstaining from the use of sugar on account of the Negro Trade, in any one else would be altogether ridiculous, but as long as the whole of your mind keeps free from spiritual pride...you may be indulged in such whims, till your mind becomes enlightened with more reason.” 5

Quakers charged with acting as unlicensed schoolteachers, but the Quakers continued to

found schools.5

It was against this background that Thomas Young began his education. Young’s

maternal grandfather, Robert Davis, advocated thorough schooling and was gratified by

his intelligent grandson. Under the tutelage of his aunt, Mary Davis, Young learned to

read English at the age of two, the Bible at four, and Latin by six.6 At the age of seven,

he was sent to “a miserable”7 Quaker boarding school, where he remained for a year and

a half before returning to his parents’ home. It was during this time that he had his first

introduction to the sciences, by reading books lent by a neighbor. After six months of

self-instruction, he was sent to Compton School in Dorset, another Quaker boarding

school much better suited to his tastes. It was run by “a Mr. Thompson, who… had the

good sense to leave his pupils some little discretion in the employment of their time.”8

Compton encouraged its students to follow their own academic interests as well as the prescribed survey of the classics. Young thus deepened his acquaintance with Latin, began his education in Greek, and had his first encounters with French, Italian and, for his own amusement, Hebrew. Even at this young age, Young pursued knowledge for its own sake, staying up late or waking up early so as to learn as much as possible.

At the age of thirteen, Young was recommended by a friend of his maternal aunt as a suitable and intelligent companion for Hudson Gurney, grandson of the wealthy Quaker merchant, David Barclay. This opportunity yielded a private tutor, years spent far from

5 Adrian Davies, The Quakers in English Society 1655-1725 (New York: Oxford University Press, 2000), 124. 6 Peacock, Life of Thomas Young, 3. 7 Victor L. Hilts, “Thomas Young’s ‘Autobiographical Sketch’,” Proceedings of the American Philosophical Society 122, 4 (1978): 250. 8 Hilts, “Thomas Young’s ‘Autobiographical Sketch’,” 251. 6

home in London and Hertfordshire, and the beginnings of what proved to be a life-long friendship with Gurney.9 The initial tutor retained for the position never arrived, forcing

the Gurneys to seek another suitable member of the Society of Friends for the position.

The eventual choice was the editor of Calligraphia Graeca, John Hodgkin, who cultivated Young and Gurney’s classical education.

At fifteen, Young contracted a probable case of tuberculosis but weathered it under the care of Dr. Richard Brocklesby, his maternal great-uncle. It is likely that this period

of proximity with the wealthy and successful London physician spurred Young’s interest

in a medical career. Brocklesby strongly encouraged his great-nephew to enter the field

and showered Young with attention and intellectual encouragement. As Young

acquainted himself with mathematics, botany, zoology – particularly entomology – and

the works of Newton, Brocklesby requested “regular reports of his literary and scientific

pursuits.”10

While little information is available about Young’s parents or grandparents, his

great-uncle was a public figure and it is easy to see how Brocklesby’s own life may have

influenced Young’s. Richard Brocklesby was born in Somersetshire to a family

belonging to the Society of Friends. Like many young Friends interested in a medical

career, Brocklesby chose to enter the University of Edinburgh in 1742, then matriculated at Leiden University and graduated in 1745 with an M.D. He moved to London, became a

Fellow of the Royal Society in 1747 and a licentiate of the Royal College of Physicians in

1751. Within the next three years, Brocklesby apparently chose to leave the Society of

9 Hudson Gurney was Young’s first biographer, after Young’s death. 10 Hilts, “Thomas Young’s ‘Autobiographical Sketch’,” 251. Young kept track of his books read each year, so it is possible to see that he read Linnaeus’ Philosophia Botanica, Simpson’s Fluxions, Newton's Principia and Optica and Bonnycastle’s Astronomy, all in the year 1790, after his bout with consumption. 7

Friends, possibly to fulfill social, political, or financial ambitions. He quickly gained a

second M.D. degree from Cambridge in 1754, and was subsequently elected a Fellow of

the College of Physicians. Surprisingly, Brocklesby then flouted the Quaker tradition of

pacifism by joining the British army as a physician in 1758 and serving in Germany

during the Seven Year’s War.11

In many respects Brocklesby was Young’s mentor, sharing his great-nephew’s early

linguistic efforts in Greek verse with renowned scholars of his acquaintance. Through

Brocklesby, for example, Young met the Duke of Richmond, who was so taken with

Young that he offered him a position as personal secretary. Young declined carefully, averring his affiliation with the Society of Friends even as the offer filled him with pride.

In his autobiography, he described his decision to turn down the opportunity as possibly

foolish, in light of his later lack of success in the practice of medicine. At the time, however, he took care to reassure his mother that he was disinterested in such worldly advancements. “I have very lately refused the pressing offer of a situation which would have been the most favorable and flattering introduction to political life that a young man in my circumstances could desire,” he wrote, “and I was not ashamed to allege my regard for our Society as a principal reason for my not accepting the proposal.”12

Medical School and Young’s First Publication

Young’s aspirations to a medical career led him to enroll in William and John

Hunter’s School of Anatomy. There he spent two years preparing himself for medical

school. While studying at the Hunterian School of Anatomy, Young’s interest in

11 “Brocklesby, Richard (1722-1797),” in vol. 2 of The Dictionary of National Biography, ed. Sir Leslie Stephen and Sir Sidney Lee (London: Oxford University Press, 1937), 1282. 12 Peacock, Life of Thomas Young, 45. 8

physiological optics began with his dissection of an ox’s eye. He noticed that its

structure was intriguingly complex and wanted to investigate the precise mechanism of

vision. His resulting paper on the subject, “Observations on Vision,” displayed his

unpracticed scholarship; it was straightforward, earnest, and slightly pedantic.

Nevertheless, the work showed understanding of the optical field as it stood in 1793 and,

with the help of Richard Brocklesby, Young submitted it to be read before the Royal

Society in May, 1793.

Young’s “Observations on Vision” contained some interesting points that caught the

attention of the Royal Society. In the paper, Young argued that the crystalline lens is muscular and that this muscularity enables the eye to focus:

From the observation of Dr. Porterfield and others, that those who have been couched13 have no longer the power of accommodating the eye to different distances, I had concluded that the rays of light, emitted by objects at a small distance, could only be brought to foci on the retina by a nearer approach of the crystalline to a spherical form and I could imagine no other power capable of producing this change than a muscularity of a part, or the whole, of its capsule.14

Immediately after the paper was submitted, John Hunter, head of the anatomy

school, claimed priority of discovery and asked to give his findings as the Croonian lecture the following year. He died before he could finish the lecture, but Sir Everard

Home continued Hunter’s research and gave the lecture on his behalf. Potentially damaging rumors flew that Young’s ideas were originally Hunter’s,15 and Home’s

experimental results directly refuted Young’s suppositions, complicating matters further.

13 "Cataract Surgery," Community Eye Health Journal 14, no. 38 (2001): 31, http://www.jceh.co.uk/0953- 6833/14/jceh_14_38_031.1.html. Couching is a process usually applied to cataract sufferers, in which the lens of the eye is dislocated towards the back (or vitreous humor). The process was surprisingly effective, though infection was a common result. 14 Thomas Young, Miscellaneous Works of the late Thomas Young (London: John Murray, 1855) 1: 4. 15 Alexander Wood, Thomas Young: Natural Philosopher, 1773-1829 (Cambridge: Cambridge University Press, 1954), 23. 9

In the face of the Hunter/Home findings – which appeared to show that even

individuals whose eyes had been couched retained ‘the power of accommodation,’ or the

ability to bring into focus objects at various distances – Young publicly withdrew his own

hypotheses. He did this first in his Göttingen Dissertation with the phrase, “Sententia

nuper de lentis crystallinœ usu in oculo ad diversas rerum videndarum distantias

accommodando proposita, neque nova erat neque vera videtur”16 and reiterated it in his

“Outlines of Experiments and Inquiries respecting Sound and Light” paper, read before

the Royal Society on January 16, 1800. In the latter, Young said, “should further

experiments tend to confute any opinions that I have suggested, I shall relinquish them

with as much readiness as I have long since abandoned the hypothesis… [of] the

functions of the crystalline lens.”17

Before Young could withdraw his hypotheses in his later publications, Brocklesby’s circle of acquaintances worked to repair the harm done to Young’s incipient scientific reputation by nominating him to the Fellowship of the Royal Society. That this effort succeeded is probably due in no small part to Everard Home’s willingness to be one of the signatories. Young was elected into the Royal Society in 1794, at the age of twenty-

one.

Quakers and University

After his election to the Royal Society, Young decided to continue his medical

studies. Subsequent to completing school, Quakers faced limited career choices. Of the

16 Young, Miscellaneous Works, 1: 1. Note by the editor, quoting p. 68 of Göttingen Dissertation published in 1796, translates loosely to “the theory of the crystalline lens being used to accommodate the vision at different distances was seen as neither new nor true.” 17 Young, Miscellaneous Works, 1: 96; Thomas Young, “Outlines of Experiments and Inquiries respecting Sound and Light,” Philosophical Transactions 90 (1800): 106. 10

three traditional professions, law, medicine and the clergy, only medicine was available

to them, and even then Quakers were excluded from English medical schools. Trade was another option, but Quaker pacifism limited those choices to the ‘innocent trades’ such as

iron-smelting and food production. For the scientifically-inclined, medicine was the most

attractive option.

Prior to the 1850s, English universities required their students to subscribe to the

1662 Thirty-Nine Articles of Anglican faith. Cambridge permitted students to enter the university without subscribing to the Articles, but not to graduate and take a degree, while Oxford required students to profess their Anglican faith upon entry to the

university. The Oxford University Act of 1854 and Cambridge University Act of 1856

both abolished oath-taking requirements upon matriculation. The Cambridge University

Act also abolished the oath requirement for students taking a degree, stating that “it shall

not be necessary for any… undergraduate student in his academical education, to make or

subscribe any declaration of his religious opinion or belief, or to take any oath, any law or

statute to the contrary notwithstanding.”18

This pair of provisions opened the door for Dissenting students to enter and graduate

from Cambridge without being forced to take any religious oaths or make any

declarations of faith to the Established Church. Dissenters were not able to take jobs at either university, but they were permitted to complete degrees. This in turn gave

Dissenters access to social networks available only to graduates of Cambridge and

Oxford, including Fellowship in the Royal College of Physicians.19

18 The UK Statute Law Database, Cambridge University Act 1856 (c.88), provision 46, http://www.statutelaw.gov.uk (accessed March 12, 2007) 19 Following the Medical Act of 1858, the Royal College of Physicians eliminated the Fellowship restrictions that favored graduates of Cambridge and Oxford 11

Before the Oxford and Cambridge University Acts of the mid 1850s, however,

English Quakers wishing to pursue medical degrees were forced to travel outside of

England, initially to the Continent and the Universities of Leiden and Padua.20 Neither

school had religious tests restricting admission, and both offered Quaker students

alternatives to the English universities. In the later eighteenth and early nineteenth

centuries, German universities such as Göttingen also attracted Dissenting medical

students. In 1726, the University of Edinburgh opened its own medical school, offering a

closer and more affordable option for English Dissenters than schooling on the Continent.

By the middle of the eighteenth century, Edinburgh was the preferred city for

Quakers to study medicine. Not only was the medical school under secular, rather than

ecclesiastical, control but Scotland was more tolerant of Dissenters than England. The

presence of established Quaker congregations in the late seventeenth century provided

additional reassurance to Quaker parents that their sons (and sometimes daughters) would

have a religious point of contact while at school.21

Pursuing a Medical Career

Young decided, therefore, to study medicine at Edinburgh. He spent only a year

there, however, before transferring to Göttingen. Given the excellence of Edinburgh’s

medical school, Young’s decision seems odd. However, Göttingen also had a superb

reputation, and Young may simply have been interested in exposure to German language

and education. To complete his medical degree at Göttingen in 1796, Young wrote a

20 Geoffrey Cantor, “Real Disabilities?: Quaker Schools as ‘Nurseries’ of Science” in Science and Dissent in England, 1688 – 1945, ed. Paul Wood (Burlington: Ashgate Publishing Company, 2004), 148. 21 Geoffrey Cantor, Quakers, Jews, and Science: Religious Responses to Modernity and the Sciences in Britain, 1650 – 1900 (New York: Oxford University Press, 2005), 64. 12

dissertation on the human voice and sound: De Corporis Humani Viribus

Conservatricibus. The dissertation was widely researched and well-praised upon its

completion, and included an alphabet of forty-seven letters intended to convey every

sound that the human voice is capable of producing.22 In addition to demonstrating

Young’s ongoing fascination with languages, this dissertation stimulated his interest in

the general properties of sound.

After his graduation from Göttingen, Young learned of new statutes passed in the

Royal College of Physicians that affected his plans to enter the profession. In order to

practice medicine in London, all physicians were required to be members of the Royal

College of Physicians. Graduates of any university could apply for permission to practice

as licentiates of the College, but only physician graduates of Cambridge and Oxford

could join as Fellows. Licentiate members were eligible for election to fellowship at the

recommendation of the President of the College and only after serving seven or more

years as a licensed member.23 Unfortunately for Young, the qualifications for

membership changed to mandate that “candidates for the licentiate must, before graduating, have spent two whole years in some respectable University.”24

Since Young spent his two years at separate universities, he was unqualified for

membership in the College. Although returning to Edinburgh for a second year was an

option, Young instead chose to enter Emmanuel College, Cambridge in the spring of

1797. Although it added an extra year to his studies, a Cambridge degree promised to

ease his path to fellowship in the Royal College of Physicians.

22 Wood, Thomas Young: Natural Philosopher, 49. 23 Wood, Thomas Young: Natural Philosopher, 54. 24 A Picture of the Present State of the Royal College of Physicians of London (London: Sherwood, Neely, and Jones, 1817), xxxiii, quoted in Wood, Thomas Young: Natural Philosopher, 54. 13

Disownment

Young’s entrance to Cambridge signified his willingness to break away from the

Society of Friends. Quaker students could enter Cambridge and attend classes, but were

required to renounce Quakerism and subscribe to the Thirty-Nine Articles of Anglican

faith in order to graduate and take a degree. Only the previous year, while at Göttingen,

Young wrote to his mother about the graduation ceremony, assuring her that “I would not

rashly give up the privileges of a member of the Society of Friends, and I have already,

on this ground, asked, and obtained leave to be admitted to a degree without an oath.”25

Given Young’s fondness for un-Quakerly entertainments such as music and theater, this

may have been a platitude for his mother or may indicate that a radical change occurred

in his attitude towards the Society of Friends after leaving Germany. In December of

1797, Richard Brocklesby died, leaving Thomas Young his London home and the

comfortable sum of £10,000. Young continued to live at Cambridge, but treated London

as his permanent residence and spent more time in society there.

In the eighteenth and nineteenth centuries most Quakers were “birthright” Quakers,

or children of two Quaker parents. It was possible to convert to the Society of Friends,

but the rate of conversions was relatively low. Conversely, it was possible to lose

membership either through voluntary resignation or through disownment, a regulated

form of expulsion. Quakers as a group seemed to have had no compunction about

expelling members of the Society for moral transgressions or failures to abide by Quaker regulations. Moral transgressions might include “immorality, dishonesty, or habitual

drunkenness,” while breaches of Quaker rules included marriage to non-members or a

25 T.J. Pettigrew, Medical Portrait Gallery (London: Fisher, Son & Co., 1840), 4:7, quoted in Wood, Thomas Young: Natural Philosopher, 56. 14

first cousin, non-attendance of meetings (usually paired with attendance of Anglican

church services), failure to abide by testimonies or bankruptcy.26 Before the 1860s, the

primary cause of disownment was marrying-out. Any member who married a non-Quaker

– accounting for between a quarter and a third of Quakers who married at all27 – was

immediately expelled. Some joined other churches, some continued to attend meetings as

non-Quakers, but the number of people affected by this was enormous for a sect the size

of the Society of Friends.28

Social Meetings and weekly worship services formed the basis of Quaker religious

life. All Quakers belonged to a Monthly Meeting, comprising several local congregations.

The Monthly Meeting was the locus of Quaker business: it received and decided upon

applications to membership, it performed expulsions, and it registered births, deaths, and

marriages. This Meeting also issued certificates of transfer to any Friend moving to the

jurisdiction of another Monthly Meeting. The issue of such a certificate meant that the

Monthly Meeting was vouching for the good conduct of the recipient, and that he or she

was free of debt and in good standing with his or her local meeting.

A young Friend setting out for a school, such as the University of Edinburgh, would

request, and usually receive, a certificate of transfer from his local Meeting. The

certifying Meeting vouched for the student’s integrity, but the receiving Meeting

accepted responsibility for ensuring the student’s spiritual and physical welfare. Upon

graduating, the student would receive another transfer certificate. If fit to continue as a

Friend, the student’s new certificate would be sent to the Meeting for his intended home.

26 Isichei, Victorian Quakers, 135. 27 Isichei, Victorian Quakers, 115. 28 Isichei, Victorian Quakers, 112. Isichei estimates that there were 60,000 Quakers in England and Wales in 1680, a number which declined to 19,800 by 1800 and then fell further to 13,859 in 1860. 15

While a student in Edinburgh, Thomas Young privately studied music and dance.

These offences might have been overlooked, but his repeated attendance of performances

at the theater and attempts to shed Quaker dress and speech were grave transgressions.29

Young flouted Quaker behavior, so the Edinburgh Meeting’s willingness to transfer

Young’s certificate is somewhat surprising. Perhaps the Edinburgh Meeting was more than usually flexible in its definition of appropriate Quakerly behaviors. If the student charges of the Meeting consistently explored the worldly delights of Edinburgh, the members of the Meeting would have been forced to generosity of interpretation. Not all meetings were so lax, however.

When a Monthly Meeting judged a member delinquent and a candidate for expulsion, it would send two “Visitors” to interview the Friend in question. If the individual did not seem contrite, the Visitors would encourage him or her to repent his or her errors. If the Visitors were successful in their exhortations, the offender would offer a written apology to the Meeting. If the offender was unrepentant, disownment quickly followed.

After Young’s matriculation at Cambridge, but before Brocklesby’s death, Young was “received as a member of Westminster Monthly Meeting by certificate from

Edinburgh (17 August 1797).”30 The Edinburgh Meeting of the Society Friends retained him as a member while he studied at Göttingen, not transferring him to the charge of another meeting until he was back in England. Less than six months after the transfer of his certificate from Edinburgh to Westminster, Young was approached by concerned members of his new Meeting.

29 Peacock, Life of Thomas Young, 59. Peacock says that Young studied music theory, learned to play the flute and took private dance lessons, in addition to attending the theater frequently. 30 “Thomas Young,” Dictionary of Quaker Biography, (Friends’ House Library, unpublished typescript). 16

On February 15, 1798, the Westminster Monthly Meeting of the Society of Friends

formally disowned Thomas Young. Like many other young Quakers, Thomas Young had

escaped the rigid confines of Quakerly behavior, and like many other young Quakers had

been caught. Young chose to pursue a lifestyle that conflicted with Quaker religious

practices, making this pivotal event inevitable. Unlike other transgressors, though, Young

was impenitent. According the Westminster Meeting minutes, he “having attended places

of public diversion was privately visited… but as he attempted to justify himself, this

meeting was informed thereof and Friends… report that they found him not disposed to

condemn his conduct but by his own acknowledgement estranged from us in principle

and practice.”31 The Westminster Meeting disowned Young for his unrepentant pursuit of

the frivolous and sinful activities of dancing and attending the theater, though his pursuit

of an Anglican education could easily have been sufficient cause.

Early Optical Experiments

With one medical degree already completed, Young rarely attended lectures at

Cambridge, instead devoting himself to social activities and scientific exploration. He also continued to study the principles of sound, performing experiments and theoretical investigations of fluid motion, vibrating strings, and musical beats.32 Young used his

observations on this broad range of sound and light phenomena to write the “Outlines of

Experiments and Inquiries respecting Sound and Light.” This paper, dated 8 July 1799

and written at Emmanuel College, Cambridge,33 took the form of a letter sent to Edward

31 Westminster Monthly Meeting Minutes, February 15, 1798. Library of the Society of Friends, London. 32 Edgar W. Morse, “Thomas Young,” in Dictionary of Scientific Biography, ed. Charles Coulston Gillispie (New York: Scribner, 1970) 14: 565. 33 Young, “Sound and Light,” 147. 17

Whitaker Gray, Secretary of the Royal Society and was read to the Royal Society the

following January. Of the sixteen sections of the paper, one – section X, entitled “Of the

Analogy between Light and Sound” – addressed the similarities between light and sound

and offered the first hint of Young’s later theories on the nature of light.

In 1799, as Young wrote his paper on light and sound, the nature of light itself

was hotly contested. On one side of the argument, emission theorists, or corpuscularists,

believed that light consisted of rays of small particles that responded to forces from

material bodies. On the other side, vibration or undulation (or wave) theorists postulated

that light was a vibration or undulation in a ubiquitous medium that they called the ether.

Isaac Newton was considered the first champion of emission theory. In his queries at the

end of the Opticks, he presented several propositions labeling light a projectile that

reacted to force. Robert Hooke, René Descartes and Christiaan Huygens were all early proponents of vibration theories, declaring that light was a wave that moved through the ether. Despite his allegiance to the emission theory, Newton also proposed the existence of a vibratory ether in which the light rays traveled.

In his “Sound and Light” paper, Young put forth some of the difficulties he perceived with the emission (or corpuscular) theory of light. He began by praising

Newton’s writings, but then proceeded to enumerate three problems he observed. First, he questioned the uniform velocity with which light moved. Was it really possible for electricity, furnaces, friction and the sun all to propel Newton’s corpuscles at the same speed? Next, he addressed the more problematic issue of simultaneous reflection and refraction. When presented with the phenomenon of bright and dark fringes in thin plates,

Newton stated that the cause was an inherent periodicity within light that he dubbed, “fits 18

of easy reflection” and “fits of easy transmission.” If light was in a fit of easy reflection, it would be reflected from the second surface and cause a light fringe, while light in a fit of easy transmission would pass through the second surface and create a dark one.34 Like many others, Young rejected Newton’s theory of fits and declared, “why, of the same kind of rays, in every circumstance precisely similar, some should always be reflected, and others transmitted, appears in this system to be wholly inexplicable.”35 Embracing

the vibratory theory of light required acceptance of the existence of a luminiferous ether

that transmitted light as air transmitted sound. Young argued in favor of its existence,

citing the phenomenon of electricity as proof. Young’s third difficulty with the emission

theory of light stemmed from the phenomenon of colors in thin plates. Young cited

Euler’s supposition that the colors of light come from differing frequencies of the

vibrations of ether, and then suggested an analogy between them and the sounds emitted

by organ pipes. With this novel interpretation, Young implied that the “periodic

appearance of colours in a thin plate might be due to the resonance effect depending on

the relation between the wave-length and the plate’s thickness, in the same way that

resonances are obtained in an organ pipe.”36

When Young reprinted the paper in volume two of his lectures, he ascribed to Euler

the sole authorship of the organ pipe analogy and removed all further discussion of the

phenomenon.37 When the original version of the paper was reprinted in Miscellaneous

Works, the editor felt compelled to interject a note disclaiming the analogy as “fanciful

34 Isaac Newton, Opticks; or, a Treatise of the Reflections, Refractions, Inflections & Colours of Light, 4th ed. (London: William Innys, 1730; reprinted with preface by I. B. Cohen, New York: Dover Publications, 1952), 281 (page citations are to the reprint edition). 35 Young, “Sound and Light,” 125-6. 36 Geoffrey Cantor, Optics after Newton: theories of Light in Britain and Ireland, 1704-1840 (Dover: Manchester University Press, 1983), 130-1. 37 Young, Miscellaneous Works, 2: 543. 19

and altogether unfounded.”38 Although the original analogy was incorrect, it was fruitful

as the first step towards formulating Young’s law of interference.

Young’s new optical experiments filled the remainder of his time at Cambridge.

Young completed his required two years at the school before returning to London in the spring of 1800 to begin his medical career. On the strength of his Göttingen degree,

Young began to practice medicine before receiving either his M.B. or M.D. from

Cambridge. Cambridge University statutes required that six years elapse between admission to the college and receipt of the degree of M.B., and that another five years elapse before a student could attain a Doctorate.39 Young was therefore unable to attain

Fellowship in the Royal College of Physicians until 1809.

Meanwhile, seven years after submitting his first paper on the subject, Young formally revisited his earlier researches on vision. The resulting paper, “On the

Mechanism of the Eye,” was read to the Royal Society in November of 1800 and published in the Philosophical Transactions of 1801. Young’s interest in the subject was renewed after reading a paper by Dr. William Porterfield,40 a well-respected Scottish

physician, and he proceeded to perform new experiments on both his own and others’

eyes. In this dense and well-researched paper, Young upheld his own original conclusions

while refuting those of Everard Home.

Referring both to the caution necessary in performing the experiments and,

obliquely, to Home’s mistaken conclusions, Young began by observing that optical

38 Young, Miscellaneous Works, 1: 81 39 Peacock, Life of Thomas Young, 211. 40 The paper was William Porterfield, “An essay concerning the motions of our eyes. Part II. Of their internal motions,” Edinburgh Medical Essays and Observations 4 (1738). Porterfield also was renowned for his A Treatise on the Eye, the Manner and Phænomena of Vision and for his work on phantom limbs, being an amputee himself. 20

experiments require great delicacy and that “no apology is necessary for the fallacies

which have misled many others, as well as myself, in the application of those

experiments to optical and physiological determinations.”41 To measure the dimension

of his own eye, Young employed a method appropriate neither for the clumsy nor the

faint of heart, but that belonged in the long tradition of scientists using themselves as

research subjects:42

For measuring the diameters (of the eye), I fix a small key on each point of a pair of compasses; and I can venture to bring the rings into immediate contact with the sclerotica… To find the axis, I turn the eye as much inwards as possible, and press one of the keys close to the sclerotica, at the external angle, till it arrives at the spot where the spectrum formed by its pressure coincides with the direction of the visual axis, and, looking in a glass, I bring the other key to the cornea…

Young then casually continued, “with an eye less prominent, this method might not

have succeeded.”43 Through careful experimentation, Young was able to disprove

three hypotheses of accommodation: that the curvature of the cornea changes; that the

length of the eyeball changes; and that both changes occur simultaneously. Again,

Young’s experiment to restrict the length of the eyeball was not for squeamish:

Another test, and a much more delicate one, was the application of the ring of a key at the external angle, when the eye was turned as much inwards as possible, and confined at the same time by a strong oval iron ring, pressed against it at the internal angle. The key was forced in as far as the sensibility of the integuements would admit, and was wedged, by a moderate pressure, between the eye and the bone.44

Even in this awkward position, his powers of accommodation were unaffected,

indicating that the underlying cause of accommodation was the fourth hypothesis: the

41 Young, Miscellaneous Works, 1: 13; Thomas Young, “The Bakerian Lecture: On the Mechanism of the Eye,” Philosophical Transactions 91 (1801): 24 42 Andrew Robinson, The Last Man who Knew Everything (New York: Pi Press, 2006), 75. 43 Young, Miscellaneous Works, 1: 25; Young, “Mechanism of the Eye,” 38. 44 Young, Miscellaneous Works, 1: 42; Young, “Mechanism of the Eye,” 59. 21

shape of the crystalline lens. Young was hard-pressed to explain the lens shape. He was

unwilling to embrace his earlier hypothesis of the lens being muscular, but he could not

entirely discard it. His conclusion therefore simply outlined the experiments and

attributed the source of clear vision to the shape of the crystalline lens.

The Royal Institution & Maturation of Young’s Optical Theories

In the summer of 1801, Young was invited by Benjamin Thompson, Count Rumford

to serve as Professor of Natural Philosophy for the Royal Institution. After some negotiation – Young suggested that the salary should be commensurate with the work involved and also should make up for the loss of income he would experience while being unable to serve as a physician – he accepted the position. He gave his first course of lectures in Natural Philosophy from January to May 1802, and gave a revised and expanded course of lectures the following spring. Unfortunately, his efforts and intelligence did not guarantee his success: he was a poor lecturer. Gurney described his lecture style as “compressed and laconic”45 and as exceeding the capacity of his

audience. Even Young himself recognized the problem and apologized to the audience at

the end of his 1802 lecture series, comparing his lectures to the early sketches of painter

preparing a canvas.46

Four months after accepting his professorship at the Royal Institution, Young

presented his first paper devoted entirely to optical phenomena, “On the Theory of Light

and Colours,” to the Royal Society. The paper was selected by the President and Council

of the Royal Society to be read as the Bakerian Lecture of 1801 on November 12, 1801.

45 Hudson Gurney, Memoir of the Life of Thomas Young (London: John & Arthur Arch., 1831), 21. 46 G.N. Cantor, “Thomas Young’s Lectures at the Royal Institution,” Notes and Records of the Royal Society of London 25 (1970) 1: 91. 22

While the work may simply have grown from his previous investigations, his exposure to

the laboratory resources and library of the Royal Institution probably enhanced it. In the

paper, Young set out a series of four hypotheses, nine propositions, and numerous

corollaries that he used to argue that light is undulatory, not corpuscular. Young took great pains to support as many of his points as possible with relevant quotes from

Newton’s work. Although this could have been a political move to help legitimize his theories, Young himself mentioned the debt owed to Newton for first proposing the theory of ether. He then acknowledged that “those who are attached, as they may be with the greatest justice, to every doctrine which is stamped with the Newtonian approbation, will probably be disposed to bestow on these considerations so much the more of their attention, as they appear to coincide more nearly with Newton's own opinions.”47

Young’s main novel contribution of the paper was his eighth proposition, which stated “When two Undulations, from different Origins, coincide either perfectly or very nearly in Direction, their joint effect is a Combination of the Motions belonging to each.”48 This proposition was an extension of an earlier argument – from the Sound and

Light paper – stating that a particle of air affected by multiple sound waves would be

subject to the vector of their combined motion. The implication of this proposition was

that undulations of the same frequency and magnitude were capable of either constructive

or destructive interference. Young did not specify the necessary physical conditions to

achieve either, but did offer the general analogy of a “beat” of light before applying the

principle of interference to five specific cases in his corollaries. These cases included the

colors of striated or scratched surfaces, the colors of thin plates – an ongoing interest for

47 Young, “Theory of Light and Colors,” 14. 48 Young, “Theory of Light and Colors,” 33. 23

Young – and the causes of blackness. Young’s discussion of striated surfaces suggested

that iridescence was the result of interference. In the case of thin plates, Young measured

the intervals at which Newton’s rings appeared to determine the wavelengths of light.

The corollary on blackness was less successful, and was removed by Young from his

1807 reprint of the paper.

Young’s final proposition, IX, stated that “Radiant Light consists in Undulations of the luminiferous Ether.” In a final bid to use Newton’s theories for support, Young argued that this proposition was the inevitable conclusion of the preceding statements and that “it is clearly granted by Newton, that there are undulations, yet he denies that they constitute light.”49 With this declaration, Young concluded a paper that proposed some

interesting ideas and professed strong support for the vibration theory but failed to

provide much in the way of experimental results. His audience would have to wait

another two years for Young to produce convincing experimental support for his theory

of interference.

Young gave his second short paper on optics the lengthy title, “An Account of Some

Cases of the Production of Colours, not Hitherto Described.” It followed on the heels of

Young’s Bakerian lecture of 1801, and was read to the Royal Society in July of 1802.

Young began the paper with a reiteration of his major proposition from the previous

work, that light waves demonstrated constructive and destructive interference.

“Wherever two portions of the same light arrive at the eye by different routes, either

exactly or very nearly in the same direction, the light becomes most intense when the

difference of the routes is any multiple of a certain length, and least intense in the

49 Young, “Theory of Light and Colors,” 44. 24

intermediate state of the interfering portions.”50 Young then added that these lengths

differed for the different colors of light.

In this second optical paper, Young attempted to provide the experimental support

that his previous paper lacked. Here, Young presented accounts of his observations of

diffraction fringes observed in fibers, of colors viewed in “mixed plates” by looking at a

candle through two plates of glass with liquid between them, and of colors observed in

thin films. Using his law of interference, Young could predict the diameter of the fringes

that appeared when light traveled through the glass plates, water and interstitial air gaps.

His predictions held when he substituted fats for water, leaving Young satisfied with his

interference explanation. In his observations of thin films, such as soap bubbles, Young

sought to explain the occurrence of a central black spot appearing when the film is at its

thinnest (i.e., just before a soap bubble bursts). The same phenomenon can also occur in

the generation of Newton’s rings. Even though the path difference should be zero, the

waves counteract each other, producing blackness. Young suggested that the reflection of

the two waves was occurring under opposing conditions: one reflection was from the rare

air into the dense glass, the other from the dense glass into the rare air. This effectively

increased the path of one wave by half of a wavelength and produced destructive

interference in the center of the rings.51 To prove his theory, Young then placed a drop of

sassafras oil between the plate and lens used to display Newton’s rings. The oil was denser than the lens, but less dense than the plate,52 and so the reflections of both waves

50 Thomas Young, “An Account of Some Cases of the Production of Colors, not Hitherto Described,” Philosophical Transactions 92 (1802): 387. 51 Young, “Colors not Hitherto Described,” 393. 52 Wood, Thomas Young: Natural Philosopher, 167. 25

occurred under the same conditions of comparable density. This produced a white center

spot, verifying his predictions.

Young delivered his third paper on optics, “Experiments and Calculations relative to Physical Optics,” to the Royal Society as a Bakerian lecture in November of 1803. In the paper, Young concisely described his most evocative and convincing experiments in optics. He began by explaining his intent to prove his proposition that “fringes of colours are produced by the interference of two portions of light.”53 He tacitly challenged

potential critics to verify his work, by labeling his experimental apparatus ‘easily

reproduced’ before describing that apparatus in detail:

I brought into the sunbeam a slip of card, about one-thirtieth of an inch in breadth, and observed its shadow, either on the wall or on other cards held at different distances. Besides the fringes of colour on each side of the shadow, the shadow itself was divided in number, according to the distance at which the shadow was observed, but leaving the middle of the shadow always white. Now these fringes were the joint effects of the portions of light passing on each side of the slip of card, and inflected, or rather diffracted, into the shadow. For, a little screen being placed a few inches from the card, so as to receive either edge of the shadow on its margin, all the fringes which had before been observed in the shadow on the wall, immediately disappeared, although the light inflected on the other side was allowed to retain its course, and although this light must have undergone any modification that the proximity of the other edge of the slip of card might have been capable of occasioning.54

Young used the measured dimensions of the observed fringes from his experimental

results to calculate the differences in path-length, or wavelength of the light. He

compared his results with those of Newton from the Opticks,55 and concluded that they

agreed satisfactorily. Young clearly wanted to establish the universality of his law of

interference. At the end of the paper, he made brief mention of recent work performed

53 Thomas Young, “The Bakerian Lecture: Experiments and Calculations Relative to Physical Optics,” Philosophical Transactions 94 (1804): 1-2. 54 Young, “Physical Optics,” 2. 55 Young made reference to the eighth and ninth observations in the third book of Newton’s Optics. 26

independently by William Hyde Wollaston and Johann Ritter on “the existence of solar

rays accompanying light, more refrangible than the violet rays, and cognisable by their

chemical effects… These rays appear to extend beyond the violet rays of the prismatic

spectrum.”56 Young, wishing to compare the properties of ultraviolet light with visible light, used a thin plate, a solar microscope, and paper dipped in silver nitrate to obtain an image of the rings produced by these waves. These rings proved to be much smaller than the bright rings of visible light, but of approximately the same dimensions as rings of violet light generated with violet glass.57 Young concluded the paper with his wistful

ambition to have sufficiently sensitive thermometers to be able to perform a similar

experiment on “the rays of invisible heat discovered by Dr. [William] Herschel.”58

Oddly, Young gave the effective conclusion to his paper close to the midpoint, after

which he continued to present experimental results. He did not explicitly state that light

was undulatory, but rather said that it was not corpuscular, directly challenging

proponents of the emission theory to disprove his findings. He then presented an analogy between light and sound:

From the experiments and calculations which have been premised, we may be allowed to infer, that homogenous light, at certain equal distances in the direction of its motion, is possessed of opposite qualities, capable of neutralising or destroying each other, and of extinguishing the light, where they happen to be united; that these qualities succeed each other alternately in successive concentric superficies, at distances which are constant for the same light, passing through the same medium. …[Therefore] since we know that sound diverges in concentric superficies, and that musical sounds consist of opposite qualities, capable of neutralising each other, and succeeding at certain equal intervals, which are different according to the difference of the note, we are fully authorised to conclude, that there must be some strong resemblance between the nature of sound and that of light.59

56 Young, “Physical Optics,” 15. 57 Young, “Physical Optics,” 15-6. 58 Young, “Physical Optics,” 16. 59 Young, “Physical Optics,”11-12. 27

Leaving the Royal Institution

Young resigned from his post with the Royal Institution in the summer of 1803, later describing his duties of professorship as “so incompatible with the pursuits of a practical physician, that, in compliance with the advice of my friends,”60 he gave notice of his

desire to resign. This may simply have been a polite cover for the deterioration of

Young’s relationship with the managers of the Royal Institution. After the departure of

Count Rumford in 1802, Young was at the mercy of the Institution’s politics. His lecture

style did not suit the Royal Institution, and his popularity waned even as fellow lecturer

Humphry Davy’s soared.

Before leaving the Royal Institution, Young had increased his involvement with the

Royal Society and in 1802 was appointed Foreign Secretary of the Royal Society, an

office he held for the rest of his life. He had resigned his professorship at the Royal

Institution, and focused his energies once again on the pursuit of a successful medical

career. In the spring of 1803, Young received his M.B. from Cambridge. The following year, Young married Eliza Maxwell. Their marriage was a happy one but they had no

children.

Young’s 1803 paper on optics proved to be his last. He continued to publish

scientific articles, but began to publish his non-medical topics anonymously. It is possible

that his concerns about his profession as a physician dissuaded him from further optical

investigations, but it is also possible that he was disheartened by the reaction of his

scientific peers.

60 Young, Miscellaneous Works, 1: 215. 28

Conflict with The Edinburgh Review

Aside from his immediate acquaintances in the British scientific community, there

seemed to be little response to Young’s three papers. A most vigorous and public

condemnation of his work, however, emerged as a series of articles in the newly formed

Edinburgh Review, the first of which appeared in 1802. Henry Brougham, a scientist and later Lord Chancellor of England, wrote these reviews. At the time of publication, however, Brougham was simply an aspiring young natural philosopher with a pen and a grudge.

In 1800, Young published an essay in the British Magazine entitled “An Essay on

Cycloidal Curves.” This essay would have elicited little note, except for three references

Young made to a paper Brougham printed in the Philosophical Transactions in 1798.61

In the paper, Brougham presented a number of solutions to geometric problems without

providing figures or diagrams, and Young was condescendingly critical of his work:

We see an author exerting all his ingenuity in order to avoid every idea that has the least tincture of geometry, when he obliges us to toil through immense volumes filled with all manner of literal characters, without a single diagram to diversify the prospect, we may observe with the less surprise that such an author appears to be confined in his conception of the most elementary doctrines, and that he fancies he has made an improvement of consequence, when, in fact, he is only viewing an old subject in a new disguise… He may very easily fancy he has made discoveries, when the same facts had been known and forgotten long before he existed. An instance of this has lately occurred to a young gentleman in Edinburgh, a man who certainly promises, in the course of time, to add considerably to our knowledge of the laws of nature. 62

John Robison, Professor of Natural Philosophy at the University of Edinburgh, took

Young to task publicly for these “admonitions to a very young and ingenious

61 The paper was Henry Brougham, Jun. Esq., “General Theorems, Chiefly Porisms, in the Higher Geometry,” Philosophical Transactions 88 (1798): 378-396. 62 Young, Miscellaneous Works, 1: 100-101. 29

gentleman”63 in an Encyclopedia Britannica article on “Temperament.” Young wrote a letter in response, which was published in Nicholson’s Journal. “According [to] the

author of this article, I have… taken the liberty of giving severe advice to a young

mathematician who never asked it,” he wrote, “I did, in fact, endeavour to show that the

gentleman in question had overlooked the labours of some former authors relative to his

subject, but I accompanied my remarks with nothing like admonition.”64

This unapologetic response did little to assuage Brougham’s anger. As one of the

founders of the Edinburgh Review, Brougham had the opportunity to publicly repay

Young for the criticisms, and did so in three separate articles, one for each optical essay

Young published in the Philosophical Transactions. As an emission theorist, Brougham

criticized Young’s findings and hypotheses, but as an anonymous reviewer, Brougham

took his criticisms into the realm of invective-filled personal attacks:

It is difficult to argue with an author whose mind is filled with a medium of so fickle and vibratory a nature. Were we to take the trouble of refuting him, he might tell us, ‘My opinion is changed, and I have abandoned that hypothesis; but here is another for you.’ We demand, if the world of science, which Newton once illuminated, is to be as changeable in its modes, as the world of taste, which is directed by the nod of a silly woman, or a pampered fop? Has the Royal Society degraded its publications into bulletins of news and fashionable theories for the ladies who attend the Royal Institution?65

Brougham seems to have taken no small pleasure in targeting Young, the Royal

Society and the Royal Institution. As time wore on, he became more scathing. The third, and most abusive, of the essays appeared in the fifth volume of the Edinburgh Review, in

1804:

63 Young, Miscellaneous Works, 1: 134. 64 Young, Miscellaneous Works, 1: 135. 65 [Henry Brougham], “The Bakerian Lecture on the Theory of Light and Colours. By Thomas Young, M.D.F.R.S. Professor of Natural Philosophy of the Royal Institution. From Philosophical Transactions for 1802. Part I,” The Edinburgh Review 1 (1802-3): 450-452. 30

In our Second Number, we exposed the absurdity of this writer’s ‘Law of interference,’ as it pleases him to call one of the most incomprehensible suppositions that we remember to have met with in the history of human hypotheses.66

We now dismiss, for the present, the feeble lucubrations of this author, in which we have searched, without success, for some traces of learning, acuteness, and ingenuity, that might compensate his evident deficiency in the powers of solid thinking, calm and patient investigation, and successful development of the laws of nature, by steady and modest observation of her operations.… From us, however, [Dr. Young] cannot claim any portion of respect, until he shall alter his mode of proceeding, or change the subject of his lucubrations.67

Young did write a reply in the form of a pamphlet, “Reply to the Animadversions of

the Edinburgh Reviewers.” In addition to defending himself against some of the more

personal attacks and explaining the progression of his research, Young attempted to

clarify the experimental results described in his papers. To some extent he was successful

in this clarification, but the pamphlet did not receive wide distribution. Young also

unveiled the author of the attacks, suggesting as he did so that Brougham’s own

qualifications as a science critic were lacking:

As far as I have discovered, the different flexibility of light is admitted, in the absurd and unwarrantable sense in which it is here employed, by three writers only. The first is Mr. Henry Brougham, the second the anonymous author of an article in the Encyclopedia Britannica, and the third the assailant whose injurious attacks I am now repelling. From so remarkable a coincidence, I think myself authorized to conclude, that these three writers are one and the same.68

Entertainingly, Young also compared the possibly deliberate misquotation of his

papers to a misprint in the Bible: “The remaining part…is as correctly quoted as that

edition of the Bible was printed, in which the only error was the omission of the word

66 [Henry Brougham], “The Bakerian Lecture. Experiments and Calculations relative to Physical Optics. By Thomas Young, M.D.F.R.S. From Phil. Trans. 1804,” The Edinburgh Review 5 (1804): 97-98. 67 [Henry Brougham], “The Bakerian Lecture,” (1804), 103. 68 Young, Miscellaneous Works, 1: 209. 31

‘not’ in the seventh Commandment.”69 In the years that lapsed after Young’s 1804 reply

to the Edinburgh Reviewers, he seemed to lose interest in optical research.

Medical Practice and Egyptology

Beginning in 1805, Young spent every summer practicing medicine in the seaside town of Worthing. Living in London during the rest of each year, Young expanded his patient list and developed his professional reputation. Young also continued to work on his course of lectures for the Royal Institution, preparing them for their 1807 publication.

In addition to being an excellent compilation of scientific knowledge, the published lectures contained the first public description of Young’s experiments on the interference of light. In 1808, Young finally received his M.D. from Cambridge and was able to obtain Fellowship in the Royal College of Physicians the following year. In 1811, Young sought an elected position as Physician to St. George’s Hospital. With three candidates vying for the position, the competition was close, but Young campaigned among all of his acquaintances and won the election. He retained his association with the hospital for

the rest of his life, even after he ceased his active practice of medicine.

Young continued to write medical articles and papers. In 1809 he presented the

Royal Society’s Croonian lecture on the functions of the heart and arteries. In the same

year, he also published a course of medical lectures that he had given at Middlesex

hospital. Young continued to write scientific articles such as his “Theory of the Tides,”

but it was not until 1814 that his attention diverted to an entirely new topic.

69 Young, Miscellaneous Works, 1: 212. 32

In 1814, Young received fragments of papyrus from Sir William Rouse

Boughton, a friend who had recently traveled to Egypt. Subsequent examination of these

fragments spurred Young’s interest in hieroglyphics, and he turned his attention to

deciphering them. The most valuable resource for the task, the Rosetta Stone, was

discovered in Egypt by the French army in 1799. It was subsequently seized by British

troops and put on display at the British Museum in 1802. The Rosetta Stone holds three

inscriptions, one Greek, one demotic and one hieroglyphic. The easily translated Greek

text proved to be a decree from Ptolemy that ended with the statement that it would be

inscribed three times, once in each script, making the stone a crucial key in deciphering

the hieroglyphics.

Young obtained copies of the inscriptions in 1814 and took them to Worthing, where

he spent the summer attempting to find a key. Even though other scholars had worked

fruitlessly for twelve years, Young seemed frustrated by his lack of immediate progress.

In an August letter to Gurney he said, “You tell me that I shall astonish the world if I make out the inscription. I think it on the contrary astonishing that it should not have

been made out already, and that I should find the task so difficult as it appears to be.”70

Despite his complaints, Young deciphered the demotic script over the course of the summer and continued to work on the hieroglyphics decipherment for the next few years.

Young did succeed in identifying the name of Ptolemy in both demotic and hieroglyphic scripts, and he suggested the phonetic construction of proper names.

In the midst of his other ongoing projects and interests, Young never did complete a translation of the Rosetta Stone inscriptions. That honor belonged to Jean-François

Champollion. Even after Champollion’s success, however, Young continued to dedicate

70 Peacock, Life of Thomas Young, 261. 33

himself to the puzzle of Egyptian hieroglyphics. His fascination remained unabated at the

end of his life. At the time of his death, Young was working on an Egyptian dictionary.

While Young first worked on his Rosetta Stone project in 1814, Macvey Napier, editor of the Encyclopedia Britannica, asked him to contribute to the new Supplement to

the Encyclopedia Britannica. Young initially declined, stating in a letter to Napier that “I

feel it a matter of necessity to abstain as much as possible from appearing before the

public as an author in any department of science not immediately medical: and even if

this objection were removed, I am not sure that I could find time to execute any task of

importance in such a way as would be satisfactory to myself."71 In 1816, Young decided

that he did have the time to write for the Encyclopedia Britannica and offered to write

some articles provided that he could contribute anonymously. He continued to focus on

medicine, preferring to write “anything of a medical nature which you [Napier] might

think desirable,” but he also suggested article topics ranging from linguistics to

meteorology to optics.72 Between 1816 and 1823, Young proceeded to write sixty-three articles for the Encyclopedia Britannica, including forty-six biographies.73 Among these

were articles on annuities, bridges, carpentry, chromatics, Egypt, languages, Malus,

Count Rumford, polarization, steam engines, tides, and weights and measures.74

71 Young to Macvey Napier, Worthing, 9th August 1814, in Peacock, Life of Thomas Young, 252. 72 Young to Macvey Napier, London, 12 February 1816, in Peacock, Life of Thomas Young, 253. The breadth of his interests are evident in the articles he offered to write for Napier: "Alphabet, Annuities, Attraction, Capillary Action, Cohesion, Colour, Dew, Egypt, Eye, Forms, Friction, Halo, Hieroglyphic, Hydraulics, Motion, Resistance, Ship, Strength, Tides, and Waves". 73 Peacock, Life of Thomas Young, 254. 74 Hilts, “Thomas Young’s ‘Autobiographical Sketch’,” 259. 34

Revisiting Optics

Although he edited his published papers and lecture notes for the 1807 publication of

his lectures, Young did not again invest significant energy in interference and the

undulatory theory of light until 1815, and then only in correspondence. As Young’s

biographer, George Peacock, said of this period, “the name of Dr. Young was ostensibly

connected with no important experimental or theoretical optical investigations. In fact his

previous labours upon the subject seemed to have been absolutely forgotten.”75 The latter

point is probably untrue given Young’s later correspondence with François Arago and

other French scientists. However, the field of optics did continue to develop without any

additional contributions from Young. Pierre-Simon Laplace published a memoir on

double polarization of Iceland spar in 1809. That same year, Etienne Louis Malus

discovered the polarization of light by reflection before going on to win an Académie des

Sciences prize competition in 1810 with his theory of double refraction of light in

crystals. Meanwhile, Sir David Brewster engaged in a variety of optical researches and

François Arago investigated the colors of crystalline plates produced by polarized light.

Despite his lack of ongoing novel contributions to the field, Young remained aware of its

developments. He reviewed Laplace’s 1809 memoir on double polarization and criticized

it for its adherence to the Newtonian corpuscular theory and for ignoring the optical work

of British scientists such as William Hyde Wollaston.76 As Foreign Secretary for the

Royal Society, Young also corresponded with foreign scientists about recent

developments in the field throughout the decade.

75 Peacock, Life of Thomas Young, 369. 76 Young, Miscellaneous Works, 1: 221-222. 35

In October 1815, Augustin Fresnel presented a paper to the Académie des

Sciences in which he described his discoveries in optics. He made these discoveries entirely independently and without any knowledge of Young’s existing papers, until

François Arago drew his attention to them in November of that year. In early 1816,

Fresnel wrote to Young and enclosed a copy of the published memoir. In his letter,

Fresnel wrote:

When I submitted it to the Institute I did not know of your experiments and deductions you drew from them, so that I presented as new explanations which you had already given long before. I have withdrawn these in the printed memoir which I now have the honour to send you and I have only left the explanation of the coloured fringes of shadows, for there I have added something to what you had already said on this phenomenon.77

He concluded, in a most conciliatory fashion, by saying:

When one believes one has made a discovery one cannot learn without regret that one has been anticipated, and I admit frankly that this was indeed my feeling when M. Arago convinced me how few of the observations in the memoir which I presented to the Institute were really new. But if anything could console me for not having the advantage of priority, it would be having been brought into contact with a scholar who has enriched physics with so many important discoveries and has contributed not a little to increase my confidence in the theory which I had adopted.78

Shortly thereafter, Arago also sent a letter to Young enclosing copy of Fresnel’s

memoir and assuring him that Fresnel had acknowledged Young’s priority of discovery and that any such claims that he had himself made were made in ignorance. He continued

by criticizing the work of Jean-Baptiste Biot, an emission theorist, and concluded with

pleasure at the opportunity to correspond with Young. 79

77 Wood, Thomas Young: Natural Philosopher, 189 (Wood provides a translation of the Young-Fresnel and Young-Arago correspondence from the original French); Young, Miscellaneous Works, 1: 376. 78 Wood, Thomas Young: Natural Philosopher, 189; Young, Miscellaneous Works, 1: 378. 79 Wood, Thomas Young: Natural Philosopher, 190; Young, Miscellaneous Works, 1: 379. 36

Young clearly responded favorably to Arago’s overture, for later that summer (of

1816) while on a visit to London, Arago and Joseph Louis Gay-Lussac, the French physical chemist, detoured to Worthing to meet Young. The meeting must have been a convivial one, for Young sent a scoldingly grateful letter to Arago the following spring complaining that Arago had not fulfilled a promise to return to Worthing before returning to France, while thanking him again for making the trip. The letter clearly continued a conversation begun at Worthing, however, and Young made two notable points. The first was a slightly condescending comment about Fresnel: “I am sincerely delighted with the success which has attended Mr. Fresnel’s labours, as I beg you will tell him; and I think that some of his proofs and illustrations very distinctly stated; but… neither I nor any of those few who were acquainted with what I had written can find a single new fact in it of the least importance.”80 Clearly Young’s interpretive abilities were not brought to bear

here, as the importance of Fresnel’s work could not be denied. Young continued on,

however, to offer a novel solution to the problem of polarization:

I have also been reflecting on the possibility of giving an imperfect explanation of the affection of light which constitutes polarisation, without departing from the genuine doctrine of undulations….It is possible to explain in this theory a transverse vibration, propagated also in the direction of the radius, and with equal velocity, the motions of the particles being in a certain constant direction with respect to that radius; and this is a polarisation. But its inconceivable minuteness suggests a doubt as to the possibility of its producing any sensible effects.81

80 Young, Miscellaneous Works, 1: 381. (Young went on to say that some of Fresnel’s results were unimpressive, having been obtained by other authors, including, notably, Henry Brougham.) 81 Young, Miscellaneous Works, 1:383. 37

Young as Bureaucrat

In 1816, Young was appointed to a committee on weights and measures. This committee, comprising mainly members of the Royal Society, was charged with determining the length of a seconds pendulum, comparing the French and British standards and ascertaining the viability of standardizing weights and measures throughout the Empire. The work later fell under the aegis of Parliament, and a formal Commission formed in 1818 to address the issues, with Young serving as Secretary of the new

Commission. In three reports, published in 1819, 1820 and 1821, the Commissioners advised against radical changes in weights and measures, decried the decimal scale

(perhaps due to its association with the French Revolutionary government) and suggested keeping the existing measurement for the standard yard.82

Later in 1818, Young was appointed to the newly reformed Commission of

Longitude as one of three requisite members of the Royal Society. He again took the position of Secretary as well as the title of Superintendent of the Nautical Almanac.

These positions provided Young with a combined salary of £400 per year, giving him the freedom to reduce the size of his medical practice. Previously, Young had been careful only to link his name with his professional work as a doctor, but his involvement with the

Board of Longitude placed him unavoidably in the public eye as a man of science and politics. Subsequently, Young felt free to link his name with his scientific and linguistic publications.

82 Peacock, Life of Thomas Young, 350-353. 38

Fresnel’s Wave Theory of Light

In 1818, Fresnel submitted a memoir on diffraction to a prize competition announced

by the Paris Academy, which he easily won. The memoir combined a principle of

Huygens that suggested that “the effect of a wave might be deduced by treating each

point on it at any given moment as the source of a new wave”83 with the interference principle that he shared with Young. He made reference to “the distinguished Dr. Thomas

Young [who] has shown by a simple and ingenious experiment that the interior fringes are produced by the meeting of rays inflected at each side of [an] opaque body”84 and continued on to explain the principle of interference. The paper was so incisive that upon reading it (in the Annales de Chimie), Young immediately wrote to Arago, saying

“Perhaps, indeed, you will suspect that I am not a little provoked to think that so immediate a consequence of the Huyghenian system, as that which Mr. Fresnel has very ingeniously deduced, should have escaped myself, when I was endeavouring to apply it to the phenomena in question.”85 Young’s back-handed compliment must have been

conveyed to Fresnel, for a flurry of effusively complimentary letters was subsequently

exchanged between the two.

The next series of letters between Fresnel and Young date from 1823, and largely

address Fresnel’s progress in the intervening years. He offered copies of his newest

memoir, bemoaned his inability to become a member of the Académie des Sciences and generally provided insights into his increasing debility due to tuberculosis. In 1824,

Young solicited Fresnel for an article on Light for the Encyclopedia Britannica, which

83 Wood, Thomas Young: Natural Philosopher, 195. 84 Augustin Fresnel, “Memoir on the Diffraction of Light,” in The Wave Theory of Light: Memoirs by Huygens, Young and Fresnel, ed. Henry Crew (New York: American Book Company, 1900), 88. 85 Young, Miscellaneous Works, 1: 388. 39

Fresnel first accepted and then declined on the basis of his health. His next letter to

Young is an interesting outpouring of frustration, focused on the insularity of the British scientific community. He claimed that they would never acknowledge his achievements but instead would ever and always give credit to their own countryman, Young:

I am not persuaded of the justice of the remark in which you would compare yourself to a tree and me to the apple which the tree has produced; …For the first explanations which occurred to me of the phenomena of diffraction and of the coloured rings, of the laws of reflection and of refraction, I have drawn from my own resources, without having read either your work or that of Huyghens… This does not, of course, entitle me to share with you Monsieur, the merit of these discoveries, which belong to you exclusively by priority… If I speak of them to you, it is only to justify my paradoxical proposition, that the apple would have come without the tree.86

While no response to this letter, nor to the embarrassed letter of retraction that followed two months later is available,87 Young did mention Fresnel’s efforts in a later hieroglyphics paper describing a trip to Paris. With typical restraint, Young granted that:

Mr. Fresnel… though he appears to have rediscovered …[and] applied [the laws of interference of light], by some refined calculations, to cases which I had almost despaired of being able to explain by them, has, on all occasions… acknowledged, with the most scrupulous justice, and the most liberal candor, the indisputable priority of my investigations.88

No further mention was made of public acknowledgement until June of 1827. Young then sent a letter to Fresnel in his role as Foreign Secretary of the Royal Society, telling

Fresnel of his pleasure in being the bearer of good news: Fresnel was awarded the Count

Rumford Prize Medal, given for the most important discovery in heat and light. As the medal was considered long-overdue, the prize sum was being supplemented with some interest, and Young pointedly stated that:

86 Wood, Thomas Young: Natural Philosopher, 199; Young, Miscellaneous Works, 1: 401-402. 87 Wood, Thomas Young: Natural Philosopher, 200. 88 Wood, Thomas Young: Natural Philosopher, 201; Young, Miscellaneous Works, 3: 287. 40

At last, then, I trust you will no longer have to complain of the neglect which your experiments have for a time undergone in this country. I should also claim some right to participate in the compliment which is tacitly paid to myself in common with you by this adjudication, but considering that more than a quarter of a century is past since my principal experiments were made, I can only feel it a sort of anticipation of posthumous fame, which I have never particularly coveted.89

Sadly, Fresnel died of tuberculosis on July 14. He was almost certainly aware of the

prize, but did not live long enough to claim it.

As the optical field continued to develop, Young was unwilling to embrace the full implications of work being done by others. In 1817, Young wrote an article on

“Chromatics” for the supplement to the Encyclopedia Britannica. In the article, Young criticized Arago’s work in polarization as being unexplainable:

The experiments of Mr. Arago… which show that light does not interfere with light polarized in a transverse direction, lead us immediately to the consideration of the general phenomena of polarisation, which cannot be said to have been by any means explained on any hypothesis respecting the nature of light. It is certainly easier to conceive a detached particle, however minute, distinguished by its different sides, and having a particular axis turned in a particular direction, than to imagine how an undulation, resembling the motion of air which constitutes sound, can have any different properties, with respect to the different planes which diverge from its path. 90

Young’s fixation on his analogy between sound and light, and his inability to extrapolate wave motion beyond the longitudinal, prevented him from considering other wave forms as explanations for polarization. In one letter to Arago, from 1817, Young did suggest that a small transverse component to a longitudinal wave might help explain polarization but did not pursue the idea himself. According to Jed Buchwald, Fresnel conceived of a similar transverse wave component and included it in an unpublished

89 Young, Miscellaneous Works, 1: 409. 90 Young, Miscellaneous Works, 1: 332. 41

version of his 1816 memoir on polarization.91 Like Young, Fresnel persisted in treating light as a longitudinal wave, but unlike Young, Fresnel eventually concluded that a purely transverse waveform was the only possible explanation for observed and predicted light behaviors. Once Fresnel suggested that transverse waves caused polarization behaviors, the full implications for ether theory proved anathema to Young. In 1823,

Young wrote an article on polarization for the Encyclopedia Britannica, in which he was

aghast:

This hypothesis of Mr. Fresnel is at least very ingenious, and may lead us to some satisfactory computations: but it is attended by one circumstance which is perfectly appalling in its consequences. The substances on which Mr. Savart made his experiments were solids only; and it is only to solids that such a lateral resistance has ever been attributed: so that if we adopted the distinctions laid down by the reviewer of the undulatory system himself, in his Lectures, it might be inferred that the luminiferous ether, pervading all space, and penetrating almost all substances, is not only highly elastic, but absolutely solid!!! 92

After expressing his outrage at the consequences of transverse waves on ether theory,

Young never again returned to optics.

Young’s Later Life

Young continued with his public service to the Board of Longitude, in his position as

Physician at St. George’s Hospital, and as Foreign Secretary to the Royal Society until his death in 1829. With these increased responsibilities in London, Young stopped traveling to Worthing; the summer of 1820 was his last. At the conclusion of the

Napoleonic wars, Young finally traveled to the continent. In 1821, he and his wife took a

91 Jed Buchwald, The Rise of the Wave Theory of Light : Optical Theory and Experiment in the Early Nineteenth Century (Chicago: University of Chicago Press, 1989), 205-212, 439. 92 Young, Miscellaneous Works, 1: 415. The article was “Phenomena of Polarisation: Being an Addition made by Dr. Young to M. Arago’s Treatise in the Polarisation of Light”, from the supplement to the Encyclopedia Britannica, written January 1823. 42

grand tour of Italy that included a stop in Paris to visit French scientific associates. In

1827, Young was deeply pleased by his election as one of eight foreign associates to the

French Academy of Science. He continued to pursue his investigations of hieroglyphics,

dabbled in the field of actuarial science, and remained a conscientious correspondent.

Young continued to work until the very end of his life. In his final illness, confined

to his bed and unable to use a pen, he continued to write his Egyptian Dictionary in pencil. When a concerned friend warned him about exhausting himself, Young replied that “it was no fatigue, but a great amusement to him” and that it would be “a great satisfaction to him never to have spent an idle day in his life.”93 Young died in May 1829

at the age of fifty-six.

93 Peacock, Life of Thomas Young, 480. 43

III. Conclusions

Impediments to Young’s Optical Theories

Thomas Young led an intellectually rich and productive life. He pursued his medical

career for over twenty-five years, attending four medical schools and institutions before

practicing medicine in two cities and publishing a series of medical lectures and a treatise on consumptive diseases. Young lectured for two years at the Royal Institution, remained an active member of the Royal Society, served on the Commission on the standardization of weights and measures and served on the Board of Longitude. In the midst of all these activities, Young deciphered portions of the Rosetta stone, defined the modulus of elasticity, explained the mechanisms of color vision and color blindness, and discovered the principle of interference of light. He was widely published and worked until the very end of his life. Why, then, did Young proceed no further in his optical studies?

Several answers to that question have been offered by Young’s biographers. First,

Young’s interests ranged so widely that he could be accused of dilettantism. This suggests the possibility that Young abandoned optics simply because he lost interest.

Second, Young was renowned for an obscure writing style which might have confused his readers. Third, and most spectacular was Young’s public clash with Henry Brougham through the forum of the Edinburgh Review, which could have damaged his scientific reputation. Any one of these could conceivably have derailed Young’s scientific career, so each is worth examination.

Andrew Robinson, Young’s most recent biographer, raised the specter of dilettantism in his The Last Man Who Knew Everything: Thomas Young, the Anonymous

Polymath Who Proved Newton Wrong, Explained How We See, Cured the Sick, and 44

Deciphered the Rosetta Stone, among Other Feats of Genius, but concluded, as indicated

in his subtitle, that Young was a polymathic genius. Even so, Young’s wide range of

intellectual pursuits could have undermined his accomplishment in all areas. He was a

polymath, but becoming a polymath requires investment in many fields of study. Young

himself admitted in his autobiographical sketch that:

He certainly thought that many hours, and even years of his life, had been occupied in pursuits that were comparatively unprofitable. But it is probably best for mankind that the researches of some investigators should be conceived within a narrow compass, while others pass more rapidly through a more extensive sphere of research.94

While it is true that Young changed his focus throughout his life, science held his

attention consistently until the 1820s. It is unlikely that Young’s interest in the subject

waned much earlier, at least given the enthusiasm with which he struck up

correspondence with Arago, Fresnel, and other French scientists on optical topics in

1814.

Young completed most of his significant optical works in the years that he was

involved with the Royal Institution as a professor. Despite an unsatisfactory conclusion to

his career at the Royal Institution, the position did afford Young two years of

employment as a professional scientist. He was able to pursue his scientific interests undistracted by the requirements of his medical career, which gave him the time, energy, and physical resources necessary to perform some of his best scientific work. Although

Young completed his “Sound and Light” paper at Cambridge while he had the time to

pursue his experimental interests, he completed his next major optical paper, “Theory of

Light and Colours,” and read it to the Royal Society only four months after he began his

position with the Royal Institution. He read his next paper, “Production of Colours, not

94 Hilts, “Autobiographical Sketch,” 254. 45

Hitherto Described,” July 1802, in the midst of his tenure at the Royal Institution. Finally,

Young read his “Physical Optics” paper in November 1803, a few months after he

resigned. Although he was no longer actively working at the Institution when he

presented this paper, he had contracted with them to provide a complete version of his

lectures for publication. Young worked on writing and editing the lectures until 1807,

suggesting that he continued to immerse himself in general scientific topics throughout

the period.

Young’s early biographies, including those of George Peacock and Alexander Wood,

and some histories, such as William Whewell’s History of the Inductive Sciences, stated that Young’s principle of interference served as irrefutable proof that light was vibratory and that his contribution to wave theory was unjustly overlooked. All three authors blamed both Young’s prolixity and obscurity of style and Young’s clash with Henry

Brougham and the Edinburgh Review.95 Young’s correspondence with other scientists

suggests that obscurity of style is not a satisfying solution to the puzzle. Young

frequently exchanged letters, advice and journal articles with his contemporaries. He had

difficulties in conveying his scientific ideas to a lay audience, which led to his departure

from the Royal Institution, but his letters to and from scientific peers suggest no such

difficulties. Although Young’s correspondents did not always agree with him – Laplace

and David Brewster were emission theorists – a review of collected letters to and from

Brewster, Laplace, Arago, and Fresnel indicates little or no confusion.96

Young and other vibration theorists considered the law of interference indisputable

evidence of the undulatory theory of light, but his theory was not universally accepted.

95 William Whewell, History of the Inductive Sciences (New York: D. Appleton & Co., 1866), 2: 111-113. 96 Young, Miscellaneous Works, 1: 359-411. 46

Despite Young’s discovery, the wave theory of light did not immediately supplant

emission theory. Some emission theorists, such as Brewster,97 were willing to embrace

his law of interference divorced from vibration theory, but they did not believe that it

conclusively proved vibration theory. Other emission theorists, such as Henry Brougham,

vehemently rejected Young’s law and its affiliation with vibration theory.

Young may well have been disheartened by the abuse he received from Brougham in

the Edinburgh Review, and fearful of a generally negative response to his anti-Newtonian

stance. Young’s biographers have suggested that his condemnation at Brougham’s hands

damaged Young’s scientific credibility to the point that his work was ignored. George

Peacock wrote:

The effect which these powerful and repeated attacks produced on the estimate of Dr. Young's scientific character was remarkable. The poison sank deep into the public mind, and found no antidote in reclamations of other journals of co-ordinate influence and authority. We consequently find that the subject of Dr. Young's researches remained absolutely unnoticed by men of science for many years.98

He continued to point out that only one copy of Young’s reply to the Edinburgh

Reviewers was sold, rendering Young’s defense ineffective. Alexander Wood argued in

the same vein, declaring that the articles “were damaging to his reputation as a physicist, but, even more serious, they were prejudicial to his reputation as a physician as well.”

Wood went on to suggest that Brougham was no scientist, contending that “readers of the

Edinburgh Review had no means of knowing that Brougham had no qualification to

97 David Brewster, “On the Laws of Polarisation and Double Refraction in Regularly Crystallized Bodies,” Philosophical Transactions of the Royal Society of London 108 (1818): 271-2. Brewster called Young’s discovery the “beautiful law of interference” and credited it with explaining many color phenomena. 98 Peacock, Life of Thomas Young, 183. 47 speak as a critic of physical theories.”99 Finally, even in a preface to the 1952 reprint of

Newton's Opticks, I. B. Cohen came to Young’s defense saying that:

Young was attacked mercilessly. The most important antagonist appears to have been Lord Brougham, in all probability the author of two anonymous discussions of Young's work in the Edinburgh Review… Had not Fresnel and Arago in France become interested in the work of Young, it seems probable that the influence of the great name of Newton would effectively have blocked any pursuit of Young's ideas – at least in England – and any further development of the wave theory of light.100

However, while it is true that Brougham wrote three exceedingly unkind reviews of

Young’s papers, it is unlikely that these reviews had the widespread effect suggested by

Young’s defenders. All three reviews appeared within the Edinburgh Review’s first year, before it became an established success. Even if widely read, they lacked the authority of a long-standing publication. At the time Brougham was publishing anonymously, but because he was not yet either Lord Chancellor or a member of the Royal Society, his name carried no particular authority. Even so, Wood’s statement that Brougham lacked scientific qualifications was untrue. Brougham practiced science – it was this activity that brought him into conflict with Young initially – and was well-versed in optical matters.

Young may have been upset by his encounter with Brougham, but it is not likely to have driven him from the study of optics. If Young’s conflict with Brougham, a potential for dilettantism and trouble conveying his optical ideas were insufficient cause for him to abandon optics, then it is time to consider other possibilities. The most significant of these are Young’s Quaker upbringing, his exposure to Quaker faith and Quaker science, and his training in the English style of mathematics.

99 Wood, Thomas Young: Natural Philosopher, 170. 100 Newton, Opticks, xii – xiii. 48

The Mathematical and Scientific Styles of the English and the French

In the late seventeenth century, Isaac Newton and Gottfried Leibniz independently developed systems of calculus. Newton thought of calculus in terms of fluxions, or rates of change, and constantly varying quantities (of lengths, areas, volumes, etc.), or fluents.

He used a notation of ‘pricked letters,’ or x and y to indicate the fluxions, and x and y to indicate the fluxions of fluxions, what today are called second differentials. Gottfried

Leibniz created different notations for his calculus, in which dx and dy stood for the smallest possible differences (or differentials) in the values x and y and ∫ dxy stood for the sum of all y values under a curve. Leibniz’s notations and terminology (differential calculus and integral calculus) are still used in modern calculus.

Newton used his fluxional calculus in his Principia, and subsequent generations of

British natural philosophers followed suit, but few could fully apply his geometrically- based calculus.101 By contrast, Leibniz’s more powerful analytical calculus was embraced on the Continent and used by French mathematicians and scientists. Pierre-

Simon Laplace embraced analytical calculus and successfully applied it to the problem of planetary gravitation first addressed by Newton. His efforts culminated in the publication of his Traité de Mécanique Céleste, a 5-volume analytical solution to questions of celestial mechanics. He paired his mathematical talent with political success and rose to positions of authority in both France’s École Polytechnique and Académie des Sciences, giving him the ability to train other mathematicians and scientists in his analytical methods. Many French members of the Laplacian school were gifted theorists and skilled

101 Cantor, Optics After Newton, 148. 49 at analytical calculus. Given the optical work Malus and Fresnel later produced, it is clear that the Laplacian program was effective.

Pierre Duhem, French physicist and philosopher, suggested that there were two kinds of scientific mind: focused, narrow and deep, represented most by the French; and ample, broad and shallow, occurring most often in the English.102 In practice, Duhem suggested that ample-minded scientists used mechanistic explanations and models to explore scientific concepts while the focused-minded scientists used abstract thought and conceptual math. Duhem’s theory is broadly stated, but not inaccurate.

Many of Young’s English contemporaries praised the French analytical calculus for its elegance and effectiveness, even as they continued to use fluxional calculus. The

English scientific community transitioned to using analytical calculus only well after the turn of the nineteenth century. Analytical calculus became widespread in England through the efforts of the student-led Analytical Society and the subsequent inclusion of analytical calculus in Cambridge University’s Mathematical Tripos in the mid-nineteenth century.103 Before that transition took place in England, however, only fluxion calculus was being taught in British schools. In addition, the comparison between mathematical styles of the English and the French tends to generalize English schools to be Anglican schools. As we shall see in the next section, Quaker schools had their own curricula to follow.

102 Pierre Duhem, The Aim and Structure of Physical Theory, 2nd ed. (Paris: Marcel Rivière & Cie., 1914; translated by Philip P. Wiener, Princeton: Princeton University Press, 1954), 87. 103 Elizabeth Garber, The Language of Physics: The Calculus and the Development of Theoretical Physics in Europe, 1750-1914 (Boston: Birkhäuser, 1999), 199. 50

Quaker Science and Quaker Schooling

Quaker spirituality is rooted in the concept of the Inner Light, or “the light that lighteth every man that cometh into the world.” (John 1:9) Each Quaker man or woman believed in this divine inner light, which represented a direct experience with God.

George Fox himself wrote that “Jesus Christ might have the pre-eminence, who enlightens, and gives grace, and faith and power. Thus, when God doth work who shall let [prevent] it? And this I knew experimentally.”104 For many Quakers, the last sentence, which emphasized direct experience, was the most important.

Quaker faith was unmediated by clergy or church hierarchy. Though all Quakers belonged to Meetings, these were social structures, not religious ones. Quaker schools and Meetings attempted to curtail access to contradictory or injurious texts while encouraging Friends to seek their own individual truths. The Quaker scientist Silvanus

Phillips Thompson argued that science and Quakerism were both pursuits of Truth, and as such were mutually supporting. Since science was a road to truth, he suggested that science was an important and worthwhile activity for devout Quakers.105

In practicing observational science, Quakers could heed their own inner light and pursue truth and morality for themselves, thus enacting a form of contemplative piety.

Through the study of nature, Quakers could witness the work of the Creator. Studying science was thought to sober the unruly schoolboy, discipline the young girl, and inculcate awe at the complexity of Creation in everyone else. Direct observation and participation was the best way to support Design arguments and discussions.

104 George Fox, “The Journal of George Fox,” in Quaker Spirituality: Selected Writings, ed. Douglas V. Steere (New York: Paulist Press, 1984), 66. 105 John Brooke and Geoffrey Cantor, Reconstructing Nature (Edinburgh: T&T Clark, 1998), 296. 51

In 1680, Thomas Lawson encouraged young Friends to study “Useful and Necessary things” such as “the Nature, Use and Service of Trees, Birds, Beasts, Fish”106 along with arithmetic, geometry, navigation, geography, and agricultural practices such as bee- keeping and plant propagation. George Fox similarly encouraged schools to teach “the nature of herbs, roots, plants and trees.”107 Clearly, the study of nature was approved as a legitimate activity for young Friends. Given the number of sanctions against other activities – games, reading plays and novels, dancing, etc. – this suggested that young

Friends would pursue nature study as an avocation. Robert Barclay was adamant about avoiding most worldly pleasures (from games, sports, comedies, cards, and drink), and in his Apology suggested instead that Friends engage in:

Innocent divertisements which may sufficiently serve for relaxation of the mind, such as for friends to visit one another; to hear and read history; to speak soberly of the present or past transactions; to follow after gardening; to use geometrical and mathematical experiments, and such other things of this nature.108

Gardening and the study of natural history were both acceptable activities, and could be scientific ones very easily. More interesting is Barclay’s suggestion of “geometrical and mathematical experiments” as entertainments. They would not have been appealing or familiar to many of his contemporaries who lacked both knowledge and the equipment necessary to pursue either.109 The one thing these suggestions did share was utility and sobriety.

106 Thomas Lawson, A Mite into the Treasury, Being a Word to Artists, Especially to Heptaechnists, the Professors of the Seven Liberal Arts, so Called, Grammar, Logick, Rhetorick, Musick, Arithmetick, Geometry, Astronomy (London: A. Sowle, 1680), 41, quoted in Wood, Thomas Young: Natural Philosopher, 150. 107 Minute of Six Weeks’ Meeting, 11 May 1675, quoted in W.C. Braithwaite, The Second Period of Quakerism (London: Macmillan, 1919), 528. 108 Barclay, An Apology for the True Christian Divinity, 511. 109 Cantor, Quakers, Jews, and Science, 232. 52

Many aspects of a traditional classical education were considered corrupt by the early Quakers. Because Greek and Latin texts were full of references to heathen gods, the

Quakers preferred to use biblical sources and Christian teachings. Learning foreign languages was, for some Friends, as frivolous and indicative of vanity as the wearing of lace and ribbons.110 Logic and rhetoric were the purview of the Established Church, novels and plays pernicious and to be avoided. By contrast, nature study was encouraged.

Engaging Quaker schoolteachers for Quaker schoolchildren ensured the right kind of education. These teachers included theology and acceptable social practice in their lessons. Education itself fostered crucial literacy skills, which were necessary for most respectable trades. Literate Quakers could also then read Quaker theology and pamphlets.

Thomas Young received a Quaker education, but a liberal one. His grandfather encouraged him to study the classics and languages, and Compton allowed him the freedom to continue their study. While a student at Compton, Young learned the art of

“turning and telescope making.”111 After leaving Compton, he decided to learn botany and added microscope making to his repertoire. All of these pursuits – botany, skilled craftsmanship and optical glass-grinding – were fine occupations for a young Quaker boy. Young’s youthful interest clearly lay in languages and the physical aspects of science, rather than in abstract mathematics or science. As an adult he succeeded in both experimental research and linguistics, but his strengths lay in observation rather than theory.

110 Richard T Vann, The Social Development of English Quakerism 1655-1755 (Cambridge: Harvard University Press, 1969), 192. “In May 1723 the (Dublin Half-Yearly) meeting noted with sorrow that ‘several friends Children and some young People are unnecessarily Enclined to, and in the practice of learning French, the method of Teaching whereof as also the learning the same as now taught having a Tendency to corrupt our youth.’” 111 Peacock, Life of Thomas Young, 6. 53

Young’s exposure to elements of a classical education also helped him later attain social acceptance within London scientific society. He studied in the same universities as many of his peers, was able to translate Latin or Greek with ease, danced well enough and enjoyed plays and music performances. Despite these social graces, Young still retained many of the behaviors associated with Quakerism. An unnamed Cambridge associate of Young’s described Young as socially awkward, saying that “he had something of the stiffness [of manner] of the Quaker remaining; and though he never said or did a rude thing, he never made use of any of the forms of politeness. Not that avoided them through affectation; his behaviour was natural without timidity and easy without boldness.”112 Still, this awkwardness made Young stand out from his non-Quaker peers.

Quakers in the Royal Society

Arthur Raistrick has made the interesting claim that “in strict proportion to their numbers, Friends have secured something like forty times their due proportion of Fellows of the Royal Society during its long history.”113 If true, this could argue for the superiority of Quaker schooling or for a general Quaker receptivity to science. Brooke and Cantor, however, found that the proportion of Quaker Fellows of the Royal Society

(FRS) was much smaller. From careful decade-by-decade analysis of FRSs, Brooke and

Cantor determined that the proportion of FRSs of Quaker descent was indeed greater than in the general population between 1670 and 1900, but that this proportion ranged widely.

Prior to the third quarter of the nineteenth century, a man of Quaker descent was less than five times as likely to be elected an FRS as a non-Quaker. At the end of the nineteenth

112 Peacock, Life of Thomas Young, 118. Peacock refrains from naming the speaker, possibly because some of the description of Young is unflattering. 113 Arthur Raistrick, Quakers in Science and Industry (New York: Philosophical Library, 1950), 221-2. 54 century the Royal Society had thirty-five times as many Quaker FRSs as the general population. At that peak, though, there were only twelve Quaker and ex-Quaker FRSs in the Society.114 Of the fifty-six115 Quaker and ex-Quaker FRSs studied by Brooke and

Cantor, twenty-nine were disowned or otherwise separated from the Society of Friends at the time of their deaths.116 More interesting than the sheer proportion of Quaker FRSs are the numbers of Quaker (and ex-Quaker) FRSs who were active scientifically and active in the Society itself.

Most Fellows of the Royal Society prior to the mid-eighteenth century lacked scientific credentials. Many treated it as a social club with the added cachet of a royal charter. Based on publication in the Philosophical Transactions or other scientific journals, however, Quakers and ex-Quakers were more active scientifically than their peers in the Society. Employing this standard, Henry G. Lyons calculated the percentage of all ‘scientifically active’ Fellows in 1830 to be 32.3%. This calculation unfortunately excluded the extraordinarily prolific Thomas Young, due to his death in 1829. Using the same date and the same standard, Brooke and Cantor calculated that 70% of the Quaker group was scientifically active.117 Publication in the Philosophical Transactions was not the only indicator of Quaker scientific activity throughout the eighteenth and nineteenth centuries since most Quakers could not access this outlet. The membership subscription for the Royal Society was high, limiting access to wealthier participants. Women were

114 Brooke and Cantor, Reconstructing Nature, 283-5. 115 Brooke and Cantor, Reconstructing Nature, 312. This number is not entirely accurate. Brooke and Cantor claim to include all Quaker and ex-Quaker FRSs born before 1862, but Richard Brocklesby, FRS 1747 and ex-Quaker is excluded from the included Appendix. 116 Brooke and Cantor, Reconstructing Nature, 285. 117 Brooke and Cantor, Reconstructing Nature, 307. 55 excluded from membership until the mid-twentieth century, and most Quakers did not live in London or possess the social standing of members of the Royal Society.

Socially, the Royal Society offered an opportunity for Quaker Fellows to network with their non-Quaker scientific peers. The Royal Society did not require its members to take any religious oaths and served its Quaker Fellows as an ostensibly religiously- neutral territory in which to discuss science. As most Fellows of the Royal Society did lack scientific credentials, one of the Society’s primary functions was patronage. A young

Fellow of the Royal Society, such as Thomas Young, could engage in social intercourse with successful scientists, medical practitioners and the aristocracy. For the ambitious,

Fellowship in the Royal Society could provide personal and professional opportunities unobtainable through other means.

Within the social structure of the Royal Society, the Quakers had their own support network in place. This is clear from the election process of the Royal Society after 1731 which required three Fellows of the Society to propose and sign a certificate supporting the prospective member. Once three signatures were obtained, the certificate was displayed at the Society for at least ten subsequent meetings. If the certificate collected sufficient signatures, the prospective membership came up for ballot. 118 Throughout these elections, Quakers and ex-Quakers supported other Quakers and ex-Quakers.

From the Society’s certificates, it is possible to trace lines of patronage even within the Quaker group. Thomas Young was supported by Richard Brocklesby, his maternal great-uncle and a former Quaker. Young in turn signed for at least four Quakers and ex-

Quakers during his tenure at the Royal Society: Robert Willan (FRS, 1809), John Sims

118 Cantor, Quakers, Jews, and Science, 110-11; Brooke and Cantor, Reconstructing Nature, 298; Henry Lyons, The Royal Society 1660-1940 (Cambridge: Cambridge University Press, 1944), 152. 56

(FRS 1814), Michael Bland (FRS 1816) and finally his close friend Hudson Gurney (FRS

1818).119 While not decisive, these signatures indicate the presence of a distinct Quaker support network.

Young As Quaker Scientist

Thomas Young was raised a Quaker, in a faith that encouraged each man and woman to seek out his or her own spiritual and worldly truths. As a youth attending Quaker schools, Young was encouraged to study useful and necessary things and to employ himself productively at all times. Young was gifted at languages and spent a great deal of time studying them. He enjoyed botany and entomology particularly, and learned the useful skills of telescope-making and microscope-making while at Compton school. Like many Quaker students, Young studied observational, empirical science rather than analytical or theoretical science.

Young was exposed to his uncle Brocklesby’s worldliness from a young age, but retained, in spite of his ambitions to join high society, many of the traits associated with

Quakers. While at Cambridge he demonstrated Quaker mannerisms, particularly in his speech and forms of address. Hudson Gurney described him as possessing an

“imperturbable resolution to effect any object on which he was engaged” as a result of being raised to believe that “the perception of what is right or wrong, to its minutest ramifications, is to be looked for in the immediate influence of a Supreme intelligence, and that therefore the individual is to act upon this, lead where it may, and compromise

119 Royal Society online archives – Election certificate records: EC/1808/14, EC/1813/14, EC/1815/23, EC/1817/19 57 nothing.”120 The picture of Young that emerges from these descriptions is of a formal, forthright, ambitious and productive man, one who maintained Quakerly behaviors even after his disownment. Young’s lingering differences may explain why Quakers created a support network within the Royal Society. If all Quakers and ex-Quakers behaved sufficiently differently from their non-Quaker peers, they would find it more difficult to integrate into the social and patronage structures of the Royal Society.

As a scientist, Young spent years experimenting on wave phenomena. He began with acoustics while attending university, investigating the properties of sound from strings and pipes. He then explored hydrodynamics, water waves and tides, before moving on to experiments with light. Although he was incapable of thinking of light as anything other than a longitudinal wave in these three papers, Young’s ability to analogize light and sound indicated his strength as an observational scientist. By considering the disparate phenomena of sound and light, he was able to convincingly relate the behaviors of beats of sound and interfering waves of light. He also created a very effective demonstration of the phenomenon for the Royal Institution lectures, relying on an analogy of water and light to demonstrate a two-slit experiment in a ripple tank. In his 1807 publication of the lectures, Young resorted to the example of throwing two stones into a pond to watch the impact of the circular waves one each other before declaring the water waves, sound waves, and the production of colors all represented the same phenomenon.

Beautiful and careful figures fill Young’s papers and lectures while trigonometry appears sparingly and the calculus is notably absent. Young preferred to use a descriptive phrase over a mathematical expression, providing pages of explanation for his included figures. This tendency contributed to his reputation as an obscure writer. His 1793 paper,

120 Gurney, Memoir of the Life of Thomas Young, 6. 58

“Observations on Vision,” contained no mathematics whatsoever, while he filled the first third of his 1800 paper that revisited the same topic, “On the Mechanism of the Eye,” with trigonometry. In his next paper, “Sound and Light,” Young provided tables of measurements and detailed figures of chords, pipes and vibrating strings. This paper focused on his observations of sound, so elaborate math was unnecessary.

Both Young’s “Physical Optics” paper and his “Colors not Hitherto described” are descriptive papers, focusing on observed experimental details and providing no analytical support. In fact, Young’s only optical paper containing any calculus is Young’s “Theory of Light and Colors.” Even then, Young used fluxion calculus only in one corollary of the paper, to support his law of interference in the case of inflected light.

Young criticized Brougham for not including geometrical arguments or figures in his

“Higher Geometry” paper of 1798. In his criticism, Young declared that “geometrical construction is very simple and easy, while it almost exceeds the powers of calculus.”121

In the same essay, he also complained of the “tedious affectation of abstraction and obscurity which unfortunately pervades the writings of many great mathematicians of a later date.”122 His complaints may have stemmed from his own difficulties with analytical calculus. In a 1798 letter to his friend John Bostock, Young wrote that “Britain is very much behind its neighbours in many branches of the mathematics; were I to apply deeply to them, I would become a disciple of the French and German school; but the field is too wide and too barren for me.”123 Even Young’s posthumous champion, William

Whewell, said that Young’s mathematical methods “possessed none of the analytical

121 Young, Miscellaneous Works, 1: 100. 122 Young, Miscellaneous Works, 1: 101. 123 Young to John Bostock, June 1798, in Peacock, Life of Thomas Young, 127. 59 elegance which, in his time, had become general in France” and that this lack prevented him from applying his principle of interference to all optical phenomena.124

When Fresnel presented his successful memoir on diffraction in 1818, he, like

Young, focused on the principle of interference. Unlike Young, Fresnel used the analytical calculus to integrate the motion of every part of a light wave. His resulting calculations addressed every case of diffraction, refraction, inflection, and addressed the mysterious puzzle of polarization as well. His basic physical theory was not superior to

Young’s, but his mathematics were.

In the end, it would seem that Young’s background as an English Quaker ill prepared him to apply rigorous, analytical, mathematical methods to optical problems. It was not just that he did not want to proceed further in optical research, but that he could not. The wide and barren field of Continental mathematics eluded him.

124 Whewell, History of the Inductive Sciences, 2: 95. 60

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