ELECTRICITY. 36l 



the hook D; at the other side of the tube a piece 

 of ivory, one inch long, is screwed, with a small 

 hole for the wire to slide into. 



To use this apparatus, fill the glass tube A with 

 gunpowder, and ram the wire B a small way into 

 the ivory tube; then connect the hook C with the 

 bottom of a large jar or battery; and when the jar, 

 &c. is charged, form a communication from the 

 hook D to the top of the jar, Sec. the discharge 

 will then take place, and the explosion of the gun- 

 powder will throw asunder the roof; and the sides, 

 front, and back will then fall down. 



The Pyramid. 



Represented Fig. 18., is designed to show the 

 same experiments as the thunder-house, and is used 

 in the same manner. When the piece A is thrown 

 out by the discharge, the upper part of the pyramid 

 falls down; it is usually made to represent a stone 

 steeple, and is composed of several pieces; by 

 which means, when the discharge is made, there 

 appears greater devastation. 



The Luminous Word. 



This experiment is exactly on the same principle 

 as Fig. 10., and the word is formed by the small 

 separations made in the tin-foil; if they were cut a 

 little round at every division, the spark would ap- 

 pear more vivid as it passed along the windings. 



It may be observed in making these experiments, 

 that the longer any word is, and the oftener the 

 tin-foil is cut, the more powerful the machine must 

 be in order to convey the spark from one end to 

 the other; because every time the passage is inter- 



