8 THE MECHANICO-CHEMJCAL 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 generaliza- 

 tion of magnetic laws. 



4 De Magnete, p. 48. 



