62. ELECTRICITY AND GALVANISM. 



had been discharged by points, instead of knobs, there 

 would have been no shock; as the rush would not have 

 been so sudden. If a jar be held to the negative conductor, 

 or that part of the machine to which the cushion is 

 usually attached, the conductor being insulated, by turn- 

 ing the winch, the electricity will be abstracted from the 

 jar, and it will then be said to be charged negatively ; 

 when, by applying the knuckle as before, a similar shocfc: 

 will be experienced by the electric fluid rushing from the 

 outside to the inside of the jar. Sometimes a number of 

 jars are connected, called a battery, a shock from which, 

 well charged, has been made to kill a large dog. There 

 are numerous amusing and instructive experiments 

 which may be performed by an electrical machine* and 

 proper apparatus, which are described in works that 

 treat expressly on this science. 



The Electropliorus, an instrument invented by M. Volta, 

 of Coma, in Italy, must not be passed by without notice. 

 This instrument consists of two circular plates, one of 

 which is made either of glass coated with sealingwax, or 

 it is a composition of resinous substances without glass, 

 but it must neither have points nor projections of any 

 kind. The other plate may be of brass, or even tin, 

 or it may be a common board of about a quarter of an 

 inch thick, coated with tinfoil, having a glass handle in 

 the centre. The first-named plate must be well rubbed 

 either with new flannel quite warm, or with prepared fur, 

 or it may be well beaten with a fox's tail, it will then be- 

 come negatively electrified ; place the other plate upon it, 



* A very cheap and simple apparatus, capable of giving a consi- 

 derable shock, may be made as follows : Take a six or eight ounce 

 phial, and having filled it about two-thirds with brass filings or turnings, 

 fix into it a cork, having a brass wire, with a knob at the end, inserted 

 in it, taking care that the extremity of the wire, or a small chain 

 attached to it, may reach the filings. Then procure a satin ribbon of 

 about a yard in length, and varnish it well on both sides ; also a piece 

 of prepared fur, so contrived as to fasten round the finger and thumb 

 of the left hand ; when, by drawing the ribbon through the finger and 

 thumb, it will become excited, and by placing the phial in such a 

 position that the knob may be touched by the ribbon, while made to 

 pass through the fingers, the electricity will be conveyed to the phial, 

 which, after the operation has been repeated eight or ten times, will 

 be sufficiently charged. 



