258 Electro- Magnetic Apparatus and Experiments. 



and represents a feebler current than the shorter arc. The only 

 objection to this arrangement is the extra room it requires. 



Fia;ure 1 



. Figure 1, represents a new form of apparatus, consisting of a 

 compound electro-magnet and electro tome ; completed April, 

 1838. a, is an ivory cheek or head, through the center of which 

 appear the extremities of the wires composing the magnet. 6, b', 

 two brass straps confining the magnet to the base board, c, &, 

 the battery connexion for the large wires, which are terminally 

 soldered to the cups with the binding screws, the soldered con- 

 nexion being underneath the base board, d, d, are the fine wire 

 terminations, the solderings being out of sight, underneath the 

 base board. The movable part of the apparatus, e, /, g^ h, k^ is 

 the electrotome. e, is a stout copper wire, passing through the 

 shaft k. One extremity of this wire dips into the mercury cup, 

 {m,) the top of which is of glass for exhibiting the spark ; the 

 base of brass is soldered to the brass strap h'. At the other ex- 

 tremity of e, is a small ball of iron, [g,) which, being attracted 

 by the magnet, gives motion to the electrotome. It is proper to 

 remark here, that the sphere of iron, g^ is not attracted by the 

 magnet with the same force as would be a piece of iron of ovoid 

 form, or what would prove still better, a cjdindrical piece, the 

 length of whose axis was considerably greater than its diameter. 



