i8o The Newly-Discovered Force. [April, 
the magnet the greater the amount of the force, is not sus- 
tained by experiment. The inconsistency is more apparent 
than aCtual, for in large magnets with large cores the elec- 
tricity, it may be supposed, is converted into magnetism 
instead of this force. A certain amount of suddenness of 
interruption is necessary to the development of the force, 
and in the large magnet of Stevens Institute a number of 
seconds — about fifteen, according to our estimate — elapse, 
after the closing of the circuit, before the magnet reaches 
its maximum, while on opening the circuit the magnetism is 
undoubtedly retained in the magnet for some time. 
In the small double magnet usually employed by Mr. 
Edison the yoke is 2 inches long and 3-i6ths of an inch 
thick. The two cores forming the magnet are 1 ^ inches 
long, each, and 3-8ths of an inch thick; the coils are 
composed of twelve layers of No. 23 insulated wire 
(Fig. 2). 
Another method of obtaining the force is by means of 
self-vibrating eleCtro-magnets of moderate size, the battery 
power remaining the same as by the previous method. In 
both methods the principle is the same, a strong interrupted 
galvanic current flowing through a small coil of moderately 
fine wire. In ordinary self-vibrating machines, used by 
physicians, the battery power is insufficient, and the core of 
the magnet is probably too large. 
One of the most convenient methods for obtaining the 
force is from an ordinary telegraph “ sounder ” (Fig. 1). 
On most sounders the extremity of the lever plays between 
the points of two limiting screws. If the upper screw be 
insulated from the brass frame which holds it, and is con- 
nected to say 10 cells of bichromate of potash or Grove 
elements, the other end of which is connected to the lever 
of the sounder, the lever will at once be set in rapid vibra- 
tion, like the magnetic interruption upon an induCtion-coil. 
The spark can be obtained by drawing the edge of a knife 
lightly across the top of the lever or from the metal at the 
base. If a wire be connected with one of the binding-screws 
the force will pass through it to any point, as the gas-pipe 
or dark box, where we can study it. 
The force may be increased by uniting a number of the 
sounders connected either with separate batteries or with 
the same battery. When the force is thus increased, it may 
be obtained without metallic contact with any part of the self- 
vibrating apparatus : there appears to be a certain area or 
field in the air through which the force flies away from the 
eleCtro-magnet, and in this field it may be captured by any 
