LIFE AND WORK OP LORD KELVIN — THOMPSON. 763 



himself estimated it at about a hundred million of years at the most. 

 In vain did the naturalists, headed by Huxley, protest. He stuck to 

 his propositions with unrelaxing tenacity but unwavering courtesy. 

 " Gentler knight never broke lance " was Huxley's dictum of his op- 

 ponent. His position was never really shaken, though the later 

 researches of Perry, and the discovery by Strutt of the degree to 

 which the constituent rocks of the earth contain radioactive matter, 

 the disgregation of which generates internal heat, may so far modify 

 the estimate as to increase somewhat the figure which he assigned. 



The completion of the second edition of Vol. I of the Thomson and 

 Tait Treatise — no more was ever published — and the collection of his 

 own scattered researches, was a work extending over some years. In 

 addition he wrote for the Encyclopaedia Britannica, of 1879, the long 

 and important articles on " Elasticity " and " Heat." 



In 1871 he was president of the British Association at its meeting 

 in Edinburgh. In his Presidential Address, which ranged lumi- 

 nously over the many branches of science within the scope of the 

 association, he propounded the suggestion that the germs of life 

 might have been brought to the earth by some meteorite. 



With the advent of electric lighting at the end of the seventies 

 Thomson's attention was naturally attracted to this branch of the 

 practical applications of science. He never had any prejudice against 

 the utilization of science for practical ends. He wrote : 



There can not be a greater mistake than that of looking superciliously upon 

 practical applications of science. The life and soul of science is its practical 

 application ; and just as the great advances in mathematics have been made 

 through the desire of discovering the solution of problems which were of a 

 highly practical kind in mathematical science, so in physical science many of 

 the gveatest advances that have been made from the beginning of the world to 

 the present time have been made in the earnest desire to turn the knowledge of 

 the properties of matter to some purpose useful to mankind. 



And so he scorned not to devise instruments and appliances for 

 commercial use. His electrometers, his galvanometers, his siphon 

 recorders, and his compasses had been made by James White, optician, 

 of Glasgow. In this firm he became a partner, taking the keenest 

 commercial interest in its operations, and frequenting the factory to 

 superintend the construction of apparatus, Xew measuring instru- 

 ments were required. He set himself to devise them, designing poten- 

 tial galvanometers, ampere gauges, and a whole series of standard 

 electric balances for electrical engineers. 



Lord Kelvin's patented inventions were very numerous. Without 

 counting in those since 1900, taken mostly in the name of Kelvin and 

 James A^Tiite, they number 56. Of these 11 relate to telegraphy, 11 

 relate to compasses and navigation apparatus, 6 relate to dynamo 

 machines or electric lamps, 25 to electric measuring instruments, 1 



