556 PHILOSOPHICAL TRANSACTIONS. [aNNO 1774. 



wires being pointed, and one of them placed before the globe, or a prime con- 

 ductor, electrified positively, the phenomena of charging the Leyden bottle will 

 be discovered by the different appearances at the ends of the wires, as at fig. 1 3. 

 If the bottle be thus placed before a conductor electrified negatively ; or the in- 

 sulated rubber to a machine ; the appearances at the ends of the wires will be 

 reversed, as on Dr. Franklin's principles they ought to be ; and thus explain his 

 theory of the Leyden phial. 



But a more simple, and beautiful analysis of the Leyden phial, hath not 

 perhaps been exhibited, than the following. Let a bottle that will hold near a 

 pint, having a long neck, about an inch in diameter, be furnished with a small 

 plate at the top ; with a valve properly secured, after the bottle is exhausted : 

 from which plate, a wire about the 8th of an inch in diameter, is to project a 

 little below the neck, and terminate with a blunt end. The top is to be covered 

 with a round brass cap, firmly fixed on, and made air-tight. The bottom of the 

 bottle should be coated with tin foil, which should be continued 3 inches up the 

 side. This bottle will charge and discharge several times in a minute ; and the 

 tin foil coating will prevent the shock from affecting the hand of the operator. 

 The phenomena of charging the Leyden bottle is elegantly explained by this 

 contrivance, and is made visible by the end of the wire, on which the appear- 

 ances vary, according as the bottle is charged, viz. positively, or negatively ; or 

 as the conductor from which it is charged, is electrified. Fig. 14, letter a, 

 shows such a bottle, charging negatively, at a conductor loaded with positive 

 electricity. Letter b shows the same bottle charging positively, at the same 

 conductor. Fig. 15, letter c, shows the bottle charging positively at a con- 

 ductor electrified negatively ; or at the insulated rubber. Letter d shows the 

 same bottle, charging negatively at the same conductor. 



^3. Of the Lateral Explosion in the Discharge of the Leyden Bottle. 

 ' Exper. 1. Having made a double circuit, the first by an iron bar, l^ inches 

 in diameter, and half an inch thick ; the 2d by 44- feet of small chain ; on dis- 

 charging a jar, containing 500 square inches of coated surface, the electricity 

 passed in both circuits, sparks being visible on the small chain in many places. 

 On making the discharge of 3 jars, containing together \6 square feet of coated- 

 surface, through 3 different chains at the same time, fig. l6, bright sparks were 

 visible in them all ; and I have not the least doubt but it would have been visible 

 in as many more. The chains were of iron and brass, of very different lengths, 

 the shortest 10 or 12 inches, the longest many feet in length. When those 

 jars were discharged through the iron bar before mentioned, together with a 

 small chain, 4 of a yard in length ; the whole chain was illumined, and covered 

 throughout with beautiful rays, like bristles, or golden hair. Having placed a 

 large jar in contact with the prime conductor, I affixed to the coating of it an 



