September 4, 1890] 



NATURE 



449 



encies, by becoming a great centre of operations, ceaselessly 

 active in fostering the unity, and developing the resources, and 

 thus maintaining and increasing the power and prosperity, of our 

 Empire. 



SECTION B. 



chemistry. 



Opening Address by Prof. T. E. Thorpe, B.Sc, Ph.D., 



F.R.S., Treas.C.S., President of the Section, 



Leeds has one most notable association with chemistry of 

 which she is justly proud. In the month of September 1767, 

 Dr. Joseph Priestley took up his abode in this town. The son 

 of a Yorkshire cloth-dresser, he was born, in 1733, at Field- 

 head, a village about six miles hence. His relatives, who were 

 strict Calvinists, on discovering his fondness for books, sent him 

 to the academy at Daventry to be trained for the ministry. In 

 spite of his poverty and of certain natural disadvantages of 

 speech and manner, he gradually acquired, more especially by 

 his controversial and theological writings, a considerable in- 

 fluence in Dissenting circles. A pressing invitation and the 

 offer of one hundred guineas a year induced him to accept an 

 invitation to take charge of the congregation of Mill Hill 

 Chapel here. He was already known to science by his " His- 

 tor}' of Electricity," and the effort was made to attach him still 

 more closely to its cause by the offer of an appointment as 

 naturalist to Cook's second expedition to the South Seas. But, 

 thanks to the intervention of some worthy ecclesiastics on the 

 •''^ard of Longitude who had the direction of the business, and 



iO, as Prof. Huxley once put it, "possibly feared that a 



cinian might undermine that piety which in the days of Com- 

 modore Trunnion so strikingly characterized sailors," he was 

 allowed to remain in Leeds, where, as he tells us in his 

 " Memoirs," he continued six years, " very happy with a liberal, 

 friendly, and harmonious congregation," to whom his services 

 (of which he was not sparing) were very acceptable. "In 

 Leeds," he says, " I had no unreasonable prejudices to contend 

 with, and I had full scope for every kind of exertion." ^ 



We have every reason to feel grateful to the " worthy ecclesi- 

 astics," since their action indirectly occasioned Priestley to turn 

 his attention to chemistry. The accident of living near a brewery 

 led him to study the properties of " fixed air," or carbonic acid, 

 which is abundantly formed in the process of fermentation, and 

 wliich at that time was the only gas whose separate and inde- 

 [lendent existence had been definitely established. From this 

 happy accident sprang that extraordinary succession of dis- 

 coveries which earned for their author the title of the Father of 

 Pneumatic Chemistry, and which were destined to completely 

 change the aspect of chemical theory and to give it a new and 

 unexpected development. 



I have been led to make this allusion to Priestley, not so 

 much on account of his connection with this place as for the 

 reason that, as it seems to me, there has been a disposition to 

 obscure his true relation to the marvellous development of che- 

 mical science which made the close of the last century memorable 

 in the history of learning. Our distinguished fellow-worker, M. 

 Berthelot, the Perpetual Secretary of the French Academy, has 

 recently published, under the title of " La Revolution Chi- 

 mique," a remarkable book, written with great skill, and with 

 all the charm of style and perspicacity which invariably charac- 

 teriees his work, in which he claims for Lavoisier a participation 

 in discoveries which we count among the chief scientific glories 

 of this country. From the eminence of M. Berthelot's position 

 in the world of science, his book is certain to receive in his own 

 country the attention which it merits, and as it is issued as one 

 of the volumes of the Bibliotheque Scientifique Internationale, 

 it will probably obtain through the medium of translations a 

 still wider circulation. I trust that I shall not be accused of 

 being unduly actuated by what Mr. Herbert Spencer terms 

 " the bias of patriotism " in deeming the present a fitting occa- 

 sion on which to bring these claims to your notice with a view 

 of determining how far they can be substantiated. 



All who are in the least degree familiir witlf the history of 

 chemical science during the last hundred years will recognize, as 

 I proceed, that the claims which M. Berthelot asserts on behalf 

 of his illustrious predecessor are not put forward for the first 



' Leeds still enjoys one of the fruits of Priestley's insatiable power of 

 uurk in her admirable Proprietary Library He seems to have suggested 

 its formation, and was its first honorary secretary. 



NO. 1088, VOL 42] 



time. Explicitly made, in fact, by Lavoisier himself, they were 

 uniformly and consistently disallowed by his contemporaries. 

 M. Berthelot now seeks to support them by additional evidence, 

 and to strengthen them with new arguments, and asks us thereby 

 to clear the memory of Lavoisier from certain grave charges 

 which lie heavily on it. You have doubtless anticipated that 

 these claims have reference to Lavoisier's position in relation to 

 the discovery of oxygen gas and the determination of the non- 

 elementary nature of water. 



The substance we now call oxygen — a name we owe to 

 Lavoisier — was discovered by Priestley on August i, 1774; he 

 obtained it, as every schoolboy knows, by the action of heat 

 upon the red oxide of mercury. We all remember the charac- 

 teristically ingenuous account which Priestley gives of the origin 

 of his discovery. M. Berthelot sees in it merely the evidence 

 of the essentially empirical character of his work. " Priestley," 

 he says, "the enemy of all theory and of every hypothesis, 

 draws no general conclusion from his beautiful discoveries, which 

 he is pleased, moreover, not without affectation, to attribute to 

 chance. He describes them in the current phraseology of the 

 period with an admixture of peculiar and incoherent ideas, and 

 he remained obstinately attached to the theory of phlogiston up 

 to his death, which occurred in 1804" (p. 40). Such a state- 

 ment is calculated to give an erroneous idea of Priestley's merit 

 as a philosopher. That the implication it contains is wholly 

 opposed to the real spirit of his work might be readily shown by 

 numerous quotations from his writings. Perhaps this will suf- 

 fice : — " It is always our endeavour, after making experiments, 

 to generalize the conclusions we draw from them, and by this 

 means to form a theory or system of principles to which all the 

 facts may be reduced, and by means of which we may be able 

 to foretell the result of future experiments." This quotation is 

 taken from the concluding chapter of his "Experiments and 

 Observations on Different Kinds of Air," in which he actually 

 seeks to draw " general conclusions " concerning the constituent 

 principles of the various gases which he himself made known to 

 us, and to show the bearing of these conclusions on the doc- 

 trine of phlogiston. That he was content to rest in the faith of 

 Stahl's great generalization, even to the end, is true, and the 

 fact is the more remarkable when we recall the absolute sincerity 

 of the man, his extraordinary receptivity, and, as he says of 

 himself, his proneness " to embrace what is generally called the 

 heterodox side of almost every question." If it is argued that 

 this merely shows Priestley's inability to appreciate theory, it 

 must be at least admitted that there is no proof that he was 

 inimical to it. His position is clearly evident from the conclud- 

 ing words of the section of his work from which I have already 

 quoted : — " This doctrine of the composition and decomposition 

 of water has been made the basis of an entirely new system of 

 chemistry, and a new set of terms has been invented and appro- 

 priated to it. It must be acknowledged that substances pos- 

 sessed of very different properties may, as I have said, be com- 

 posed of the same elements in different proportions and different 

 modes of combination. It cannot, therefore, be said to be 

 absolutely impossible but that water may be composed of these 

 two elements or any other. But then the supposition should 

 not be admitted without /r^*?/"; and if a former theory will suf- 

 ficiently account for all the facts there is no occasion to have 

 recourse to a new one, attended with no peculiar advantage Uoc. 

 cit., p. 543). ... I should not feel much reluctance to adopt 

 the nrw doctrine, provided any new and stronger evidence be 

 produced for it. But though I have given all the attention that 

 I can to the experiments of M. Lavoisier, &c., I think that 

 they admit of the easiest explanation on the old system " {loc. cit., 



P- 563). 



The fact that Priestley was the first to consciously isolate 

 oxygen is not contested by M. Berthelot, although he is careful 

 to point out, what is not denied, that the exact date of the dis- 

 covery depends on Priestley's own statement, and that his first 

 publication of it was made in a work published in London in 1 775. 

 It was known before Priestley's famous experiment that the red 

 oxide of mercury, originally formed by heating the metal in con- 

 tact with air, would again yield mercury by the simple action of 

 heat and without the intervention of any reducing agent. Bayen, 

 six months before the date of Priestley's discovery, had observed 

 that a gas was thus disengaged, but he gave no description of its 

 nature, contenting himself merely by pointing out the analogy 

 which his experiments appeared to possess to those of Lavoisier 

 on the existence of an elastic fluid in certain substances. After- 

 wards, when the facts were established, Bayen drew attention to 



