ELECTRICAL APPARATUS. 265 



instrument is an improvement upon Yolta's, it being more 

 susceptible. It consists, as the cut represents, of a simple 

 gold leaf electrometer, the top of which is a flat metallic 

 plate, marked A, of a similar plate, B, which has a glass 

 handle, and of a third plate, c, also with a glass handle. 

 The plates c and B are covered on their under-sides with 

 sealing-wax varnish. To use the instrument ; first put the 

 plate B upon A, touch the plate B with the finger, and then, 

 before the finger is removed, touch the plate A with the 

 object to be tested. Take away the object, and also the 

 finger ; take up B by its handle ; place c on B, and touch c 

 with the finger. By this a portion of the electric fluid is 

 disturbed in c, so that c becomes electrified plus, or minus, 

 in the same manner as A. Place B upon A, and touch B 

 with the finger, and apply the edge of c to A ; the electricity 

 of c will then flow to A. Remove c, take the finger from B, 

 and raise B from A. Proceed in the same manner for three 

 or four times more, until so much electricity is accumulated 

 in A as to occasion the divergence of the gold leaves. 



Price, $5.00. 



Fig. 28, 



The Universal Discharger. (Fig. 286, as above.) An in- 

 strument that will be found convenient in a great variety 

 of experiments in which the electrical battery is to be used. 

 It consists of a flat board, about fifteen inches long, four 

 broad, and one thick, having two glass pillars cemented in 

 two holes upon the board, and furnished at top with brass 

 caps, each of which has a turning joint, and supports a 

 spring tube, through which the wires slide. Each of the 

 caps is composed of three pieces of brass, connected so that 

 the wires, besides their sliding through the sockets, have a 

 horizontal and vertical motion. Each of the wires is fur- 

 nished with an open ring at one end, and at the other it has 

 a brass ball, which, by a short spring socket, is slipped upon 

 the pointed extremity, and may be removed. There is a 

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