259 



of heat, electricity, and magnetism. Among these may be men- 

 tioned a masterly article in which he has shown the compati- 

 bility of the ordinary mathematical theory of statical electricity 

 with various phenomena which had been supposed by some 

 to militate against it ; his deduction from mathematical prin- 

 ciples of Faraday's law relating to the motion of a small paramag- 

 netic or diamagnetic body in a magnetic field; and his method 

 of electrical images, first communicated to the public at the 

 meeting of the British Association at Oxford in 1847, by which he 

 is enabled in an extremely simple and elegant manner to solve a 

 variety of important problems relating to the distribution of electri- 

 city on conductors. - 



Called to the Chair of Natural Philosophy in the University of 

 Glasgow in the year 1846, he has ever since continued to devote 

 himself to science in the intervals of his necessary occupations, and 

 has worked especially at his favourite subjects of heat and electricity. 



Carnot long since developed the mathematical theory of the motive 

 power of heat in a clear and satisfactory manner, assuming as an 

 axiom the indestructibility of heat. But the important researches 

 of Mr. Joule have shown that this axiom must be abandoned, for 

 that heat and work are mutually convertible. The establishment of 

 this point necessitated a reconstruction of the mathematical theory 

 of the motive power of heat, a theory of much practical importance 

 from its direct bearing on the steam-engine, and this task Professor 

 Thomson accomplished in a series of papers published in the ' Edin- 

 burgh Transactions.' 



Professor Thomson and Mr. Joule have for a long time been 

 working together, and they are now engaged in a series of experi- 

 mental researches on the thermal effects of fluids in motion. The 

 expenses attending the prosecution of these researches have been 

 defrayed by donations from the Government Grant, and the results 

 already obtained, drawn up partly in the form of short provisional 

 accounts, have appeared in the ' Philosophical Transactions ' and in 

 the ' Proceedings of the Royal Society. 5 



In connexion with this subject may be mentioned Professor 

 Thomson's remarkable speculation as to the cause of the light and 

 heat of the sun, which he refers to the impact of meteoric bodies 

 circulating around that luminary and continually falling in. The 



