LIFE AND WORK OF LORD KELVIN — THOMPSON. 753 



of unit mass of the working substance, he gave precise mathematical 

 proof of the theorem that the efficiency of the perfect engine working 

 between given temperatures is inversely proportional to the absolute 

 temperature. In collaboration with Joule he worked at the " Ther- 

 mal effects of fluids in motion," the results appearing between the 

 years 1852 and 1862 in a series of four papers in the Philosophical 

 Transactions, and four others in the Proceedings of the Royal Soci- 

 ety. Thus were the foundations of thermodynamics laid. This bril- 

 liant development and generalization of the subject (which had 

 grown with startling rapidity from the moment when Helmholtz de- 

 nied perpetual motion and Thomson grasped the conception of the 

 absolute zero) did not content Thomson. He must follow its appli- 

 cations to human needs and the cosmic consequences it involved. And 

 so he not only suggested the process of refrigeration by the sudden 

 expansion of compressed cooled air, but propounded the doctrine of 

 the dissipation of energy. If the availability of the energy in a hot 

 body be proportional to its absolute temperature, it follows that as 

 the earth and the sun — nay, the whole solar system itself — cool down 

 toward one uniform level of temperature, all life must perish and all 

 energ}^ become unavailable. This far-reaching conclusion '^ once more 

 suggested the question of a beginning, a question which, as already 

 remarked, had arisen in the consideration of the Fourier doctrine of 

 the flow of heat. 



In 1852, at the age of 28, William Thomson married Margaret 

 Crum and resigned his Cambridge fellowship. The happiness of his 

 life was, however, shadowed by his wife's precarious health, necessi- 

 tating residence abroad at various times. In the summer of 1855 

 they stayed at Kreutznach, from which place Thomson wrote to 

 Helmholtz, inviting him to come to England in September to attend 

 the British Association meeting at Glasgow. He assured Helmholtz 

 that his presence would be one of the most interesting events of the 

 gathering, so that he hoped to see him on this gi'ound, but also looked 

 forward with the greatest pleasure to the opportunity of making his 

 acquaintance, as he had desired this ever since the Conservation of 

 Energy had come into his hands. Accordingly, on July 29 Helmholtz 

 left Konigsberg for Kreutznach, to make the acquaintance of Thom- 



" " There is at present in the material world a universal tendency to the dissi- 

 pation of mechanical energy. Within a finite period of time past the earth 

 must have been and within a finite period of time to come the earth must again 

 be unfit for the habitation of man as at present constituted, unless operations 

 have been or are to be performed which are impossible under the laws to which 

 the linown operations going on at present in the material world are subject." 

 (Mathematical and Physical Papers, Vol. I, p. 514.) 



