344 BLECTRICITY. 



If gold or silver leaf be put between cards, and 

 a strong charge passed through it, it will be com- 

 pletely fused, and even reduced to the state of 

 an oxide, which will be distinctly marked upon 

 the card. 



The Electrophones. 



This simple species of electrical machine consists 

 of two plates (Plate 20. fig. 5.) A and B, made 

 of a circular form, from six to eighteen inches 

 diameter, or upwards. The upper plate is gene- 

 rally made of brass; but a tin plate, with a wire 

 turned in upon its edge, will answer exceedingly 

 well. At the centre of this plate there is a socket 

 O, in which a glass handle I, nine or ten inches 

 long, is fixed. A thin board, covered with tin- 

 foil, and suspended by silken strings, will answer 

 well, when the electrophorus is wanted of a large 

 diameter. 



The under plate may be made of glass, sealing- 

 wax, or of the following composition, viz. four 

 parts rosin, three parts pitch, three parts shell-lac, 

 two parts Venice turpentine, melted together over 

 a gentle fire. It may be poured and spread upon 

 a thin linen cloth about one-fourth of an inch 

 thick. The linen cloth must be stretched upon a 

 hoop, and made as tight as possible. If the sur- 

 face be a little rough, it will be no worse. 



The manner of using this machine is as follows: 

 rub the coated side of the under plate A with new 

 fine flannel, or a hare or cat's skin; and when it is 

 excited as much as possible, set it on a table, and 

 place the upper plate upon it, and put your finger 

 on the upper plate; then remove your finger, and 

 take hold of the top of the glass handle I, and applv 



