1908] on the Scientific WorTc of Lord Kelvin. 237 



and the experimental confirmations of several most surprising: con- 

 clusions deduced from Carnot's axiom, point in the same direction." 



We have seen the hints and principles thrown out by Thomson 

 in such profusion fructify in patient development by other e^reat 

 investigators, so that it would be difficult to name a branch of modern 

 physical science in which his activity has not been fundamental. In 

 one phase of his thous^ht it becomes cosmical, and transcends experi- 

 mental aids. All throus^h life his ideas were wont to range over the 

 immensities of the material universe, reaching back to its origin and 

 onward to its ultimate fate. In his youth he established the cardinal 

 principle of inanimate cosmic evohition, as effected through the 

 degradation of energy, which determines the fate of worlds, and is the 

 complement of the principle of evolution in organic life which came 

 to light at about the same time. In another aspect of this principle, 

 asserting that the trend of available energy must always be downwards, 

 it has developed into the key to the course and the equilibrium of 

 voltaic and chemical change, and to all other branches of physical 

 knowledge in which the atomic nature of matter is the pervading 

 influence. The greatness of the revolution thus effected in physical 

 science, and in its industrial applications which are in strict relation 

 to this available energy, requires no emphasis. The magnitude of the 

 advance brought by the mere enunciation of the principle of dissipa- 

 tion is to be measured by the very inevitableness of this law to our 

 present modes of thought ; it is difficult now to recognise the limita- 

 tions that must have belonged to the time when its formulation caused 

 such surprise and wonder. 



At the end of his strenuous career his thoughts reverted again to 

 these problems of the origin and destiny of material things. Novel 

 considerations were brought to bear, with intellectual vigour appro- 

 priate to youth, to demonstrate even the finiteness of the material 

 universe — such, for example, as the darkness of the firmament and the 

 moderate magnitude of the relative velocities of the most distant 

 stars. In the last weeks, he pondered over the remote history of our 

 own planet, and reasoned with striking force and lucidity, as may be 

 read in a posthumous paper, on the antiquity of its continents and 

 oceans, reaching back possibly to the time when the Moon separated 

 from the Earth. 



In this sketch the chief aim has been to set out a connected 

 historical view of the course of Lord Kelvin's scientific activity and 

 its relation to his contemporaries. No attempt has been made to 

 describe the charm of his personality. That has been recognised long 

 ago by the whole world ; for many a year the ordinary restrictions of 

 nationality have had little application to him ; he has been venerated 

 and acclaimed wherever scientific investigation is appreciated. No 

 instance in his long career can be recalled in which he asserted for 

 himself any claim of priority in intellectual achievement ; rather his 



