CALORIC AND ELECTRICITY. 441 



stated by Dr. Priestley, that electricity escapes 

 through some species of glass, like water through 

 a sieve, (History of Electricity, p. 592) ; and 

 there is a medical electrician in New York, by 

 the name of Humbert, who often amuses his 

 friends by discharging a Leyden jar of immense 

 size, through the coats of the glass without frac- 

 turing it. Besides, if a metallic wire be inserted 

 into a glass receiver, exhausted of air, and con- 

 nected with an electrical machine in action, a 

 stream of electric light is seen to proceed from 

 the wire in a straight line to the plate of the air- 

 pump : but if a conductor be presented to the 

 side of the glass, the electric light is drawn to- 

 wards it, which shows that electricity is attracted 

 through glass. The same thing is true, to a cer- 

 tain extent, of sealing wax, as shown by Dufay 

 a hundred years ago ; it is therefore evident, 

 that all bodies are permeable to this subtile aether. 

 The rapid passage of electricity through con- 

 ductors, and its power of communicating a shock, 

 are the most remarkable properties which dis- 

 tinguish it from caloric. But this difference 

 vanishes when we perceive, that it is only elec- 

 tricity of a peculiar tension or concentration, that 

 exhibits these powers ; and that many of its forms 

 produce no such effects. That the passage of 

 electricity through living bodies, without pro- 

 ducing the sensation of heat, is chiefly owing to 

 its velocity, would appear from the fact, that a 



