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ROBERT BOYLE1

Robert Boyle (1627–1673), the fourteenth child of the , spent a majority of his life conducting scientific research, especially in and . He was a founding member of the Royal Society (1663), an early and particularly influential learned society. Using an air pump, he performed countless experiments on the nature of air and gasses. He is primarily known for the discovery of his namesake law, which describes the inversely proportional relationship between and volume of any (assuming constant ). The passage below is taken from a public lecture by Thomas Edward Thorpe (1845–1925), a British . Click here for a link to the text.

The last experiment that Boyle describes is one of the most important and striking in the whole series, since by means of it he demonstrated how dependent the boiling point of a upon the is. Having boiled some water “a pretty while that by the heat it might be freed from the latitant air,” he placed it, whilst still hot, within the receiver, when, on exhaustion, it again began to boil “as if it had stood over a very quick fire. . . .2 Once, when the air had been drawn out, the liquor did, upon a single exsuction, boil so long with prodigiously vast bubbles that the effervescence lasted almost as long as was requisite for the rehearsing of a Pater Noster.3 “This experiment,” he says, “seems to teach that the air by its stronger or weaker pressure in ay very much modify (as the school men4 speak) divers of the operations of that vehement and tumultuous agitation of the small parts of bodies, wherein the nature of heat seems chiefly, if not solely, to consist.” Such is a very rapid and a very imperfect summary of this great work. I have purposely quoted very largely from it, for I wished to show you, in Boyle’s own words, how wonderfully near much of the philosophy of the seventeenth century is to that which we are too apt to regard as the outcome of the nineteenth. It is impossible to exaggerate the importance of Boyle’s labours; they served to give a marvelous sharpness to the notions of that time concerning the materiality of the air and of the phenomena which depend upon its . The work exhibits in an eminent degree Boyle’s character as an investigator, his quick perception and receptive mind, his great power of co-ordination, his insight, his logic, his patient care and scrupulous accuracy. It exhibits, too, his weakness; for it must be admitted that it is wanting in that grasp of principle and faculty of generalisation which we see in the work of the illustrious author of the Novum Organum5. It lacks, too, the Forsclierblick6 and power of divination so characteristic of the genius of Newton. But to say

1 Edward Thorpe, Essays in Historical Chemistry (: Macmillan and Co., 1911), 20-25. 2 Omission in original text. 3 The Lord’s Prayer. 4 Scholastic philosophers of the Middle Ages. 5 A philosophical work on logic written by . 6 German for “researcher’s eye.” 2 that Boyle is only inferior to Bacon and Newton is to assign him one of the first niches in the Walhalla of the heroes of . But Boyle’s work, as I have before hinted, was not allowed to go forth unchallenged; and the Elaterists7 were quickly taken to task, on the one hand by one Franciscus Linus8, and on the other by a far more important personage , of Malmesbury. Hobbes has been styled the subtlest dialectician of his time, and a master of precise and luminous language; too frequently, however, that language lost more in elegance than it gained in . Hobbes, although not a professed Peripatetic9 or a Cartesian, was a very pronounced Plenist.10 He utterly failed to see any virtue in the new philosophy, and the disparagement of the Gresham set, or “the experimentarian philosophers,” as he sneeringly called them, was the chief design of his Dialogus Physicus de Natura Aeris,11 the book in which he attempts to write down Boyle and his work. Boyle hated contention; but he and his friends felt that the new doctrines were at stake. It is unnecessary for me to take up your time by examining Mr. Hobbes’s arguments or Boyle’s refutation of them; it is sufficient to say that Mr. Hobbes, who had, with singular indiscretion, laid himself open by quoting Vespasian’s law, “That it is unlawful to give ill language first but civil and lawful to return it” was taught politeness and much sound philosophy. The world will willingly let the Dialogus die, or remember it only in connection with Boyle’s Examen of it. We cannot, however, so summarily dismiss Franciscus Linus. Linus sets out to prove that the in the Torricellian experiment12 is upheld not by the pressure of the air but by a certain nondescript internal cord; and Boyle undertakes to show that this hypothesis of an internal funiculus,13 which he remarks, with quiet humour, “seems to some more difficult to conceive than any of the phenomena in controversy is to be explained without it, is ‘partly precarious, partly unintelligible, partly insufficient, and besides needless.’” Indeed the matter is scarcely worth mention except for the circumstance that it gave an occasion to Boyle to return to the question, which we have seen had already interested him, of the relation between the volume and the pressure of the air. In the answer to Linus he gives two new experiments touching the measure of the force of the spring of air compressed and dilated. The account of these memorable experiments must be given in Boyle’s own words; “We took a long glass tube, which, by a dexterous hand and the help of a lamp, was in such a manner crooked at the bottom, that the part turned up was almost parallel to the rest of the tube, and the orifice of this shorter leg of the syphon (if I may so call the whole instrument) being hermetically sealed, the length of it was divided into inches (each of which was subdivided into eight parts) by a straight list of paper, which, containing those divisions, was carefully pasted all along it. Then putting in as much as served to fill the arch or bended part of the syphon that the mercury standing in a level might reach in one leg to the bottom of the divided paper, and just to the

7 Elaterists, or “elastick philosophers,” like Boyle, accounted for physical phenomena with reference to the elasticity of air. 8 A Jesuit scientist who challenged Newton’s theories and Boyle’s law of . 9 Aristotelian. 10 One who believes that all space is full of matter. 11 A work that attacked Boyle and others who were forming a society for scientific research. 12 The rise in the liquid of a tube, as in the barometer, is due to atmospheric pressure. 13 Latin for “slender rope.” 3 same height or horizontal line in the other, we took care, by frequently inclining the tube, so that the air might freely pass from one leg into the other by the sides of the mercury (we took, I say, care), that the air at last included in the shorter cylinder should be of the same laxity with the rest of the air about it. This done, we began to pour quicksilver into the longer leg of the syphon, which, by its pressing up that in the shorter leg, did by degrees straighten the included air; and continuing this pouring in of quicksilver till the air in the shorter leg was by condensation reduced to take up but half the space it possessed (I say possessed, not filled) before, we cast out eyes upon the longer leg of the glass, upon which we likewise pasted a slip of paper carefully divided into inches and parts, and we observed, not without delight and satisfaction, that the quicksilver in that longer part of the tube was 29 inches higher than the other. Now this observation does both very well agree with and confirm our hypothesis, will be easily discerned by him that takes notice of what we teacher and Monsieur Pascal and our English friend’s [Mr. Townley’s] experiments prove, that the greater the weight is that leans upon the air, the more forcible is its endeavor of dilution, and consequently its power of resistance (as other springs are stronger then bent by greater ). For this being considered, it will appear to agree rarely well with the hypothesis, and that as according to it the air in that degree of density, and correspondent measure of resistance, to which the weight of the incumbent atmosphere had brought it, was unable to counter balance and resist the pressure of the mercurial cylinder of about 29 inches, as we are taught by the Torricellian experiment; so here the same air being brought to a degree of density about twice as great as that it had before, obtains a spring twice as strong as formerly. As may appear by its being able to sustain or resist a cylinder of 29 inches in the longer tube, together with the weight of the atmospherical cylinder that leaned upon those 29 inches of mercury; and, as we just now inferred from the Torricellian experiment, was equivalent to them.” At this stage in the experiments the tube broke, and it was only after several mischances that Boyle was able to complete his observations. He then proceeded to the converse experiment—that is, to determine the spring of rarefied air. A tube, about 6 feet in length, and sealed at one end, was nearly filled with mercury, and into it was placed a “slender glass pipe of about the bigness of a swan’s quill, and open at both ends; all along of which was pasted a narrow list of paper, divided into inches and half-quarters. This slender pipe being thrust down into the greater tube almost filled with quicksilver, the glass helped to make it to the top of the tube; and the quicksilver getting in at the lower orifice of the pipe filled it up till the mercury included in that was near about a level with the surface of the surrounding mercury in the tube. There being, as near as we could guess, little more than an inch of the slender pipe left above the surface of the restagnant mercury, and consequently unfilled therewith, the prominent orifice was carefully closed with sealing-wax melted; after which the pipe was let alone for a while that the air, dilated a little by the heat of the wax, might, upon refrigeration, be reduced to its wanted density. And then we observed, by the help of the above-mentioned list of paper, whether we had not included somewhat more or somewhat less than an inch of air; and in either case we were fain to rectify the error by a small hole made (with a heated pin) in the wax, and afterward closed up again. Having thus included a just inch of air, we lifted up the slender pipe by degrees, till the air was dilated to an inch, an inch and a half, two inches, etc., and observed in inches and eights of the air’s expansion, was impelled above the surface of the restagnant mercury in the tube. The observations being ended, we 4 presently made the Torricellian experiment with the above mentioned great tube of 6 feet long, that we might know the height of the mercurial cylinder for that particular day and hour, which height we found to be 29¾ inches.”