THE PROGRESS OF SCIENCE 



5i7 



William Thomson 

 in 1854. 



in falling to a lower temperature or 

 may diffuse passively. But in 1844 

 Joule had made known his experiments 

 establishing the transformation of heat 

 into work, and in 1847 Helmholtz had 

 published his classical memoir on the 

 conservation of energy. Mayer's earlier 

 paper was first brought to general 

 notice by Joule in 1849. Maxwell pub- 

 lished his first paper in 1856, but did 

 not reach the electric theory of light 

 until eight years later. Clausius pre- 

 sented his paper on the motive power 

 of heat to the Berlin Academy in 1850. 

 It was indeed a marvelous period in 

 the history of physics. Among the 

 giants of those days, Thomson stands 

 almost or quite preeminent. His great 

 paper on the dynamical theory of heat 

 was published in 1851, and laid firmly 

 the foundations of the scientific treat- 

 ment of energy. 



In 1849 Thomson published his me- 

 moir on the mathematical theory of 

 magnetism, on which subject he had 

 already written four years earlier. This 

 was followed by his remarkable con- 

 tributions to the theory of electricity 

 and light. In later years his attention 

 was directed to the structure of the 

 ether and of matter. His limitation of 

 the age of the earth gave much concern 



to geologists and biologists, which the 

 more recent advances of physics has 

 again relieved, though the episode was 

 probably of advantage to the natural 

 sciences. 



Even in the briefest note, reference 

 should be made to Thomson and Tait's 

 " Treatise on Natural Philosophy," an 

 epoch-making text, which Helmholtz 

 translated into German, and to the 

 admirable popular lectures which fill 

 three volumes. The contributions to 

 electrical engineering have already 

 been mentioned. Thomson was the 

 leader in the advances by which steam 

 is being supplanted by electricity. 



An adequate appreciation of Kelvin's 

 personality is quoted by Sir Joseph 

 Larmor from the address of Lord Rose- 

 berry when installed as Kelvin's suc- 

 cessor in the chancellorship of the 

 University of Glasgow : " In my per- 

 sonal intercourse with Lord Kelvin, 

 what struck me was his tenacity, his 

 laboriousness, his indefatigable humil- 

 ity. In him was visible none of the 

 superciliousness or scorn which some- 

 times embarrass the strongest intel- 

 lects. Without condescension, he placed 

 himself at once on a level with his 



William Thomson 

 in 1877. 



