104 



SCIENTIFIC THOUGHT. 



of heat by friction and percussion, that heat is not 

 matter, but " may be defined a peculiar " motion, prob- 

 ably a vibration, 1 of the corpuscles of bodies tending 

 to separate them. Eumford's and Davy's memoirs 

 referred to belong to the last years of the eighteenth 

 century. Dr Young, in his celebrated lectures on natural 

 philosophy, discussing the experiments of Euniford and 

 Davy came to the conclusion " that heat is a quality, 

 and that this quality can only be motion." He refers 

 to Newton's view " that heat consists in a minute 

 vibratory motion of the particles of bodies," and to 

 his own undulatory theory of light. This analogy 

 with light seems to have for a long time served to 

 unify the speculations 2 of those who were inclined to 



1 See his " Essay on Heat, Light, 

 and the Combinations of Light," 

 which appeared in Beddoes' ' Con- 

 tributions to Physical and Medical 

 Knowledge,' 1799. This essay 

 Davy soon after condemned as " in- 

 fant chemical speculations," from 

 which he turned away to ex- 

 perimental work, remarking that 

 chemical knowledge was yet too 

 incomplete to allow of generalisa- 

 tions, and that the "first step 

 will be the decomposition of those 

 bodies which are at present un- 

 decompounded. '" This was written 

 in 1799. In 1800 (30th March) 

 Volta's invention of the " pile " 

 was communicated to the Royal 

 Society, and on the 30th April of 

 that year the first pile was con- 

 structed in this country. See the 

 first and second volumes of Davy's 

 'Collected Works,' London, 1839. 

 Davy's first publication on voltaic 

 electricity appeared in the Septem- 

 bernumberof 'Nicholson's Journal.' 

 Though the speculations of Davy 

 on heat and light, in which heat 



is conceived to be motion and light 

 (strangely) to be material, were dis- 

 carded by him, they attracted the 

 attention of Franklin and of Count 

 Rumford. Davy states that his 

 experiments on the generation of 

 heat "were made long before the 

 publication of Count Rumford's 

 ingenious paper on the heat pro- 

 duced by friction" (loc. cit., vol. 

 ii. p. 117). In spite of his own 

 refusal to follow up the lines of 

 thought suggested by them, they 

 were probably the cause of Davy's 

 appointment as lecturer on chem- 

 istry at the Royal Institution : see 

 vol. i. p. 83 ; also Memoir of Count 

 Rumford ('Works,' vol. i. 417), 

 and Paris's ' Life of Davy,' vol. i. 

 p. 112, &c. Tait, in 'Recent Ad- 

 vances,' gives a full account of 

 Rumford's and of Davy's work. 



2 See 'Young's Lectures,' 51 and 

 52. In the second edition, pub- 

 lished by Kelland forty years after 

 the Lectures were delivered, the 

 editor makes the following signifi- 

 cant remark : " The theory of heat 



