106 Experimental Philosophy. [Lecture 8. 



this manner some French philosophers conveyed 

 the electric fire through a circuit of three miles. 

 Though water is a conductor, yet, not being so 

 powerful as metals, the late Dr. Watson con- 

 veyed (as has already been observed) the electric 

 fire, by means of a wire, through the Thames, 

 and it set fire to spirit of wine on the opposite 

 side. 



The most powerful means, however, of accu- 

 mulating the electric fluid is found to be the 

 Leyden phial. This discovery was made about 

 the year 1745, by Mr. Von Kleist, dean of the 

 cathedral of Camnin. He found that a nail or a 

 piece , of iron wire, inclosed in an apothecary's 

 phial, and exposed to the prime conductor, had 

 a power of accumulating the electric virtue, so as 

 to produce the most remarkable effects ; and he 

 soon after ascertained that a small quantity of 

 fluid added to it increased the power. The fact 

 is, that if glass is coated on one side with any 

 conducting substance, that substance will accu- 

 mulate the electrical matter, because it is inter- 

 cepted by the glass, and prevented from diffusing 

 itself; the form of the glass is of little conse- 

 quence. The Leyden phial or jar, as at present 

 employed, is a thin cylindrical glass vessel, such 

 as fig. 39, about four inches in diameter, and 

 coated within and without, to within two inches 

 of the top, with tin-foil or any conducting sub- 

 stance. Within the jar is a metal wire, with a 

 knob at the top of it, which wire communicates 



