EPOCHS IN THE HISTORY OF THE CONTEMPLATION O* 



and " electric attraction" ( 528 ) were first employed, is the 

 work to which I have already so often referred, published 

 in 1600, and entitled "Physiology of Magnets, and of the 

 Earth as a, great Magnet" (de magno magnete tellure). 

 " The faculty of attracting, when rubbed, light substances, 

 whatever may be their nature, does not," says Gilbert, 

 " belong exclusively to amber, which is a condensed earth- 

 juice thrown up by the waves of the sea, and in which flying 

 insects, ants, and worms, are inclosed as in perpetual tombs, 

 (asternis sepulchris). The attracting power belongs to a whole 

 class of very different substances ; such as glass, sulphur, 

 sealing wax and all resins, rock crystal, and all kinds of 

 precious stones, alum and rock salt." The strength of the 

 ejectricity excited was measured by Gilbert by means of an 

 iron needle (not very small), moving freely on a point (ver- 

 sorium electricum) : very similar to the apparatus employed 

 by Haiiy and by Brewster, in trying the electricity excited 

 in different minerals by warmth and friction. 



Gilbert says farther on, that " friction is found to produce 

 more effect in dry than in damp air, and that rubbing with 

 silk is most advantageous. The terrestrial globe is held 

 together as by an electric force (?) (Globus telluris per se 

 electrice congregatur et cohseret) ; for the electric action 

 tends to produce the cohesion of matter (motus electricus 

 est motus- coacervationis materise)." In these obscure 

 axioms is expressed the view of a telluric electricity, the 

 manifestation of a force like magnetism belonging to matter 

 as such. Nothing was yet said of repulsion, or of the 

 difference between insulators and conductors. 



The ingenious discoverer of the air-pump, Otto von 



