258 Ellectro-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.~ 
Figure 1. 
Figure 1, represents a. new form of apparatus, consisting of a 
compound cleetro-magnet and . electrotome ; completed April, 
1838. a, isan ivory cheek or head, through the center of which 
appear the extremities of the wires composing the magnet. 4, 0’, 
two brass straps confining the magnet to the base board. ¢, ¢; 
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 apparatits, e, f, 2, fh, &; is 
the electrotome. e, is a stout copper wire, passing through the 
shaft k. One satiny of this wire dips into the mercury CUP, 
oe the top of which is of glass for exhibiting the spark ; the 
base of brass is soldered to the brass strap b’, At the other ex- 
tremity of e, isa small ball of iron, (g,) which, being attracted 
by the magnet, gives motion to the eleetrotome. © 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 cylindrical piece, the 
length of. whose axis was considerably greater than its diameter. 
