502 Prof. Thomson on tlie Uniform Motion of Heat 



lead was removed. The aqueous solution, when free from sul- 

 phide of lead, on being sufficiently concentrated, yielded crystals 

 of fraxinine on standing for a few days in a cool place. 1 ope- 

 rated on 3 lbs. of ash-bark exactly in the way just described. 

 The impure ciystals obtained from the aqueous solution were 

 dried with blotting-paper, and when crystallized out of spirits 

 of wine, were colom-less. They had lost their bitter, and had 

 acquired a sweetish taste. They had all the characteristics of 

 mannite ; and when they were subjected to analysis the following 

 were the results : — 



0-273 grm. substance, dried at 212° F., gave 0-194 grm. of 

 water, and 0-389 grm. of carbonic acid. 



Calculated. Found. 



182 100-0 100-000 



The so-called fraxinine therefore is merely mannite. The 



reason why previous experimenters had mistaken it for a new 



bitter principle was simply this, that they had not freed it 

 entirely from adhering impui-ities. 



LXXX. On the Uniform Motion of Heat in Homogeneous Solid 

 Bodies, and its connexion with the Mathematical Theory of 

 Electricity*. By Professor William Thomson. 



[O INCE the following article was written f, the writer finds 



^^ that most of his ideas have been anticipated by M. Chasles 



in two memoirs in the Journal de Mathematique ; the fii'st in 



* This paper first appeared anonymously in the Cambridge Mathema- 

 tical Journal in February, 1842. The text is reprinted without alteration 

 or addition. All the foot notes ai'e of the present date (March 1854). The 

 general conclusions established in it show that the laws of distribution of 

 electric or magnetic force in any case whatever must be identical with the 

 laws of distril)ution of the lines of motion of heat in certain perfectly 

 defined circumstances. With developments and a])plications contained in 

 a subsequent paper on the Elementary Laws of Statical Electricity (Cam- 

 bridge and Dublin Mathem. Jouni. Nov. 1845), they constitute a full theory 

 of the characteristics of lines of force, which have been so admirably inves- 

 tigated experimentally by Faraday, and complete the analogy with the theoiy 

 of the conduction of heat, of which such terms as " conducting power for 

 lines of force" (Exp. Res. §§ 27^7-2802) involve the idea. 



t This preliminary notice was written some months later than the text 

 which follows, and was communicated to the editor of the journal to be 

 prefixed to the ))a])er, which had been in his hands since the month of Sep- 

 tember, 1 84 1 . The ideas in which the author had ascertained he had been 

 anticipated by M. Chasles, were those by which ho was led to the determi- 



