102 Experimental Philosophy. [Lecture 8. 



electrics ; such are amber, jet, sulphur, glass, and 

 all precious stones ; all resinous substances ; and 

 t)-e clvjj-1 parts of animals (except the bones), 

 such ( as ,ha.ir, wool, silk, &c. On the contrary, 

 stony sijbst<mc^s in general, fluids in general, 

 alum, pyrites, sulphuric acid, black lead, char- 

 coal, and all kinds of metals are among the non- 

 electrics, or those which conduct the electric fluid. 



Soon after the discoveries, as above related, of 

 Mr. Grey, both the English and German philo- 

 sophers contrived means of accumulating the 

 electric matter and increasing its effects. Not 

 only the electric fire was rendered visible, but it 

 was made to pass from one conducting body to 

 another. Spirits and other inflammable matters 

 were easily set on fire by the electric spark ; and 

 animal bodies were made to feel what is called 

 the electric shock that is, the uneasy sensation 

 felt on the electric fluid passing through any part 

 of our bodies. 



The machines at first constructed for pro- 

 ducing the electric fire were made in a very com 

 plex form. It is now found that it may be ex- 

 cited by much simpler means; and the machine 

 exhibited in plate 9 (fig. 35.), though extremely 

 simple, is very powerful. In this figure ABC 

 represents the board on which the machine is 

 placed. D and E are two vertical supports, 

 which sustain the glass cylinder F G H I. The 

 axis of the cap K, in which the cylinder is fixed, 

 passes through the support D, and it is turned 



