NA TURE 



613 



THURSDAY, OCTOBER 24, i{ 



JAMES PRESCOTT JOULE. 



THROUGHOUT the world of science there has spread 

 a feeling of profound regret at the death of Mr. 

 Joule, which was announced a week ago in the columns 

 of Nature. On the evening of the nth of this month 

 he passed away at his residence in Wardle Street, Sale, 

 near Manchester. For many years past he was in very 

 feeble health. Indeed, as long ago as 1872 it was known 

 publicly that he was far from strong. In that year he 

 was President-elect of the British Association, but before 

 the time of the autumn meeting he was obliged to relin- 

 quish the honour on account of physical weakness ; and 

 Prof. Williamson was called upon to occupy the position. 

 In recent years Mr. Joule was living in complete re- 

 tirement, carrying on, so far as his health would permit, 

 such observations and experiments as could be con- 

 ducted without bodily fatigue ; and during this period he 

 was able to edit with occasional brief notes, the two 

 volumes of his collected papers which have been pub- 

 lished by the Physical Society of London. The first of 

 these important volumes appeared in 1884, and was 

 noticed in Nature (vol. xxx. p. 27). The second was 

 published in 1887 (see Nature, vol. xxxv. p. 461), and 

 contained the papers which Joule wrote jointly with Dr. 

 Scoresby, Sir Lyon Playfair, and Sir William Thomson. 

 At the end of the latter volume there is a list of no less 

 than 115 contributions to the various scientific societies 

 and journals which were enriched by communications from 

 his pen. The papers of Joule are remarkable in form as 

 they are in substance. Of mathematics there is scarcely a 

 line ; but they are models of clearness, of depth, and of 

 penetration into the hidden things of Nature ; and the 

 mathematician finds the experimental results stated and 

 arranged in such a manner as to lend themselves readily 

 to representation in mathematical symbols. Of experi- 

 menting he was a perfect master — full of elegant device, 

 and clear in mind as to points of difficulty and places 

 ■where error might creep in. That which, in the hands 

 of almost anyone else, would have proved too difficult to 

 lead to a trustworthy conclusion, in his hands was often 

 made to yield an important law or generalization, or to 

 afford an accurate numerical result. 



In Nature (vol. xxvi. p. 617) there appeared a bio- 

 graphical sketch of Mr. Joule ; a few words may, how- 

 ever, be permitted here, in order to fulfil our duty to one 

 of the greatest scientific leaders of the present century. 



His work, taken as a whole, and without considering 

 the relative importance to physical discoveries — that is to 

 say, judged by the originality of the objects, and the 

 means employed, the philosophic direction, the patient 

 and persevering labour, and the results obtained — would 

 be such as to place him in the front rank of philosophers. 

 If account be taken of the importance and generality of 

 his discoveries, as shown by their influence on the philo- 

 sophical thought and material progress of the v/orld, 

 then, as the discoverer of the law that energy is in 

 the same degree as indestructible and uncreatable as 

 matter, it is with Newton and Dalton that he finds his 

 placejn the history of physical science. 

 Vol. XL. — No. 1043. 



The law of the conservation of energy, which in all 

 schools of science, even the most elementary, is now 

 taught as the foundation of each and all the branches of 

 physical science — mechanics, physics, and chemistry — 

 was, in 1841, as far from recognition as at any time since the 

 discoveries of Newton had shown that, in their observed 

 motions, the heavenly bodies strictly obeyed the laws of 

 motion. The properties of friction, internal and external, 

 with which it was found necessary to endow terrestrial 

 material, and which properties were apparently nothing 

 less than those of destroying energy, were still as far 

 from explanation as the property of gravitation itself; 

 while the continued production in the steam-engine of 

 energy from the same material by the agency of heat, 

 without any consumption of heat, as was then not only 

 supposed, but counted as proved by the equality of the 

 heat received from the boiler and discharged into the 

 condenser, showed apparently nothing less than the 

 creation of energy. 



The study of heat which had taken place in the mean- 

 time had done nothing to remove these difficulties, for 

 the observed fact that heat was susceptible of quantitative 

 measurement, independent of temperature, had led to 

 the hypothesis that heat was an imponderable substance 

 — "caloric" — capable of penetrating matter and altering 

 its temperature and state, but neither creatable nor de- 

 structible. The discoveries of electric phenomena tended 

 to strengthen the caloric hypothesis by affording another 

 imponderable substance. Nor was it only such difficulties 

 in the way of the acceptance of the conservation of 

 energy which kept back its discovery. 



Energy, as a measure of mechanical potency, had 

 never assumed a prominent place in mechanical philo- 

 sophy, while the action by which it is converted into 

 motion against resistance, had scarcely been recognized 

 as a general measure of mechanical action, so that when, 

 as continually happened, the idea of heat being a me- 

 chanical action thrust itself forward, there was no distinct 

 measure of mechanical action at hand in which to gauge 

 the equivalent. 



Outside the schools of mechanical philosophy engineers 

 engaged in constructing and using the steam-engine had 

 long been led to recognize motion against resistance 

 as the mechanical and commercial measure of potency. 

 Under the names " work " and " accumulated work," these 

 men had become famihar with what are now known as 

 work and energy (actual and potential). It may be 

 noticed that Rumford first recognized the true nature of 

 the relation between heat and mechanical action by 

 observing that two horses working steadily produced 

 heat at a steady rate, but he did not reduce his results 

 further; while Joule was so familiar with the action work, 

 that he never hesitated as to the nature of the relation. 



It is true that at the time when Joule commenced his 

 work, not only had mechanical philosophy, as applied to 

 astronomy and such abstractions as frictionless and per- 

 fectly elastic matter, reached to nearly its highest level, 

 but the other branches of physical science, studied in- 

 dependently, were fast approaching their present stages. 

 Dalton's discoveries of chemical equivalents had been 

 made thirty years before, and chemistry had been 

 advancing by leaps and bounds. The phenomena of 

 electricity had been subject to the masterly handling of 



D D 



