The Significance of John Theophilus Desaguliers's Course of Experimental Philosophy to the History of Hydraulics and What It R

James W.P. Campbell The Significance of John Theophilus Desaguliers’s Course of Experimental Philosophy to the History of Hydraulics and what it reveals about the First Pump-driven Fountains James W.P. Campbell Department of Architecture, University of Cambridge, UK Summary The design of water features and fountains, and the use of waterwheels for power were well advanced in the late seventeenth and early eighteenth centuries, but the scientific and engineering literature generally lagged behind practice. Those involved in water engineering in the late Medieval and Renaissance periods had generally trained by working under existing experts and must have relied on rules of thumb and while there were books produced on fountain design they were notably lacking in technical detail. The problems associated with fountain design were to do with problems of flow. Fountains up until the end of the seventeenth century were invariably driven by reservoirs at some height above the gardens. The pressure was created by potential difference and the problems the fountain designer was interested in were how many spouts could be fed from the reservoir at a time, how dramatic they would be, and how long they would operate for before the reservoir ran dry. There were also, of course, much more practical matters to do with the design and manufacture of pipes and of spouts and valves to control them and dealing with air pockets and the surges in pressure caused by turning the system on and off, and then for those places not blessed with a high hill on which to place a reservoir above the garden, there were problems of pumping water into cisterns that could carry out the same purpose, albeit for a shorter time. Histories of Hydraulics and Fluid Dynamics tend to dwell on those books and writers whose work moved the theory forward [1]. Thus they tend to discuss Simon Stevin (1548-1620), Galileo Galilei (1564-1642), Benedetto Casteli (1577-1644), Evangelista Torrecelli (1608-1647), Isaac Newton (1642-1727), Gottfreid LeibniZ (1646-1717), Daniel Bernouli (1700-1782) and Leonhard Euler (1707-1783). While there is no doubting the long-term significance of these figures, there is a risk of overlooking those who wrote more accessible and down-to-earth treatises that were more influential at the time. To such a cannon belongs the works of French writers Edme Mariotte (1620-1684), Antoine Parent (1666-1716), Bernard Forest de Belidor (1693- 1761) and most importantly for this paper, the work of French-born English writer John Theophilus Desaguliers (1683-1744). While the other aforementioned authors all make it into the standard histories of hydraulics, Desaguliers does not get a single mention, despite the fact that his books were influential at the time and, as this paper will show, contain important information on contemporary practice which is not available from any other source. This paper will begin with a brief introduction to Desaguliers and his works on hydraulics before focusing on his most important work, volume II of his Course of Experimental Philosophy which as the title suggests began life as a series of public lectures and was published in 1744 towards the end of his life and subsequently translated and reprinted several times. 331 The Significance of John Theophilus Desaguliers’s Course of Experimental Philosophy to the History of Hydraulics and what it reveals about the First Pump-driven Fountains John Theophilus Desaguliers (1683-1744) Figure 1. Engraved portrait of John Theophilus Desaguliers, artist unknown Despite being a prominent figure in the early eighteenth century, comparatively little has been written on the life of John Theophilius Desaguliers. The most complete study is the 339-page biography by Dr Audrey Carpenter that appeared in 2011 [2]. Much of the previous work had concentrated on his connections with Freemasonry [3]. Desaguliers was an important figure in the history of Freemasonry but this has all too often tended to overshadow and detract from his more important contributions in the popularisation of Newtonian science and this area is now beginning to get more serious attention, in particular with Andrew Morris’s paper on Desagulier’s contribution towards the understanding of water wheels in his Course of Experimental Philosophy, the subject of the current paper [4]. This papers grows out of two small notes in works on the building of the great fountains at Herrenhausen for George II which as we shall see are much more important than the authors of those works suggested [5]. Desaguliers was born Jean-Théophile Desaguliers on 12 March 1683 in La Rochelle on the Atlantic coast of France, son of a French Protestant minister [6]. His father had already fled to Guernsey to escape the Huguenot persecutions and his mother followed, presumably as soon as the child was old enough to travel, certainly within a few months of his birth [7]. When the boy was nine the family moved to London [8]. His early education was probably at home and on moving to London, his father set up a French school in Islington which his son attended. Tragically his father died in 1699 and for reasons still not entirely understood, but presumably through some 332 James W.P. Campbell family connection, Desauliers finished his schooling in Warwickshire in a school in Sutton Coldfield managed by an A.M. Sanders [9]. The young man seems to have been taken under the wing the local Wilkins family and sent to Christ Church Oxford as a servitor, probably to accompany the son of the household. This gave Desaguliers access to a University education which would have been otherwise unavailable to a person in his social situation. The University was only open to those of the Anglican faith, which Desaguliers seems to have readily embraced, becoming ordained in 1710 [10]. Desaguliers appears to have been a brilliant student and was enamoured by the lectures of John Keill, who lectured on Newton’s Principia. When Keill left the University in 1709 Desaguliers continued them, moving to Hart Hall and it was there he obtained his MA in 1712. Shortly afterwards he moved to London [11]. The reason for leaving was almost certainly to marry (Fellows of Oxbridge colleges were not allowed to marry in the seventeenth century). He married Joanna Pudsey on 14 October 1712 at St Paul’s Church Shadwell and they lived first off Fleet Street and then in Channel Row in Westminster [12]. Public Lecturer The only two Universities in England before the nineteenth century were Oxford and Cambridge. Thus moving to London as a lecturer, Desaguliers had no choice if he wished to continue but to offer private lectures. His language skills came in useful in this regard as he could lecture and teach equally in English, French, and Latin [13]. His breakthrough came in 1714 when he was hired to become demonstrator for the Royal Society, a position that had been held many years before by Robert Hooke and which involved organising experiments for their weekly lectures [14]. At this time Desagulier’s great hero, Isaac Newton, was President. It was presumably both the success of these lectures and the prestige of the position that led to the invitation to lecture to the King and his family [15]. In 1717 Desaguliers temporarily decamped to Hampton Court to lecture George I and his family in French [16]. In 1719 Oxford awarded Desaguliers a Doctor of Common Laws degree (DCL) presumably in recognition of his growing prestige which he used to obtain the equivalent degree in Cambridge and enabled him to go by the title Dr Desaguliers [17]. Membership of the Royal Society probably led to Deaguliers meeting his first and most important patron, James Brydges, the 1st Duke of Chandos. Chandos appointed Desaguliers to the living of St Lawrence, Little Stanmore close to Cannons, his seat and Desaguliers helped the Duke design the water gardens there, advise on his investments with the York Buildings Company (which supplied London with water from the Thames) and with helping to drain his mines. It was to the Duke that Desaguliers dedicated his translation of Mariotte’s book on hydraulics in 1718 [18]. Publication of Translation of Mariotte Edme Mariotte (1620-1684) came from a family of civil servants and inherited the title Sieur de ChaZeuil. He joined the Academy of Sciences at its foundation and was very actively involved, publishing papers on subjects as varied as colour, trumpet notes, recoil in guns and falling bodies [19]. In France he is chiefly known for having published in 1679 in his Essais de Physique, what is known in England as “Boyle’s Law”: the volume of gas is inversely proportional to pressure [20]. In his lifetime Mariotte published doZens of books and articles [21]. He had prepared his book on hydraulics, Traité du mouvement des eaux et des autres corps fluides. Divisé en V. parties, but died in 1684, having entrusted the manuscript to Philipe De la Hire (1640-1718) who saw it through to publication in 1686. De la Hire says in his introduction, he felt that he should publish it without addition or editing and thus we can presume it was very much as Mariotte had intended [22]. Mariotte’s book as the full title suggests, was divided into five parts. These are essentially five separate essays: the first discusses the sources of water and springs, the second problems of pressure and fluids at rest; the third looks at measuring running water and spouts; the fourth the height of jets; and the fifth at pipes and networks of distribution. 333 The Significance of John Theophilus Desaguliers’s Course of Experimental Philosophy to the History of Hydraulics and what it reveals about the First Pump-driven Fountains Unlike De Hire, Desaguliers was not content to publish Marriotte’s book entirely unaltered.

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