THE MECHANICO-CHEMICAL SCIENCES. 



electric force attracts all light bodies, while the 

 magnetic force attracts iron only ; and he devises 

 a satisfactory apparatus by which this is shown. 

 He gives 4 a considerable list of bodies which possess 

 the electric property ; " Not only amber and agate 

 attract small bodies, as some think, but diamond, 

 sapphire, carbuncle, opal, amethyst, Bristol gem, 

 beryl, crystal, glass, glass of antimony, spar of 

 various kinds, sulphur, mastic, sealing-wax," and 

 other substances which he mentions. Even his spe- 

 culations on the general laws of these phenomena, 

 though vague and erroneous, as at that period was 

 unavoidable, do him no discredit when compared 

 with the doctrines of his successors a century and 

 a half afterwards. But such speculations belong 

 to a succeeding part of this history. 



In treating of these Sciences, I will speak of 

 Electricity in the first place ; although it is thus 

 separated by the interposition of Magnetism from 

 the succeeding subjects (Galvanism, &c.) with which 

 its alliance seems, at first sight, the closest, and 

 although some general notions of the laws of mag- 

 nets were obtained at an earlier period than a 

 knowledge of the corresponding relations of electric 

 phenomena: for the theory of electric attraction 

 and repulsion is somewhat more simple than of 

 magnetic ; was, in fact, the first obtained ; and was 

 of use in suggesting and confirming the general i/.a- 

 tion of magnetic laws. 



4 DC Magnele, p. 48. 



