iSz The Newly-Discovered Force. [April, 
metal of considerable surface that is brought near, even 
when it does not touch the apparatus. 
These experiments, together with others to be subsequently 
described, make it probable that only a very small quantity 
of the force is captured by the conductors thus far employed, 
the greater quantity being diffused through the air. Hence 
I have made the suggestion, which in time will be carried 
out, to enclose a number of the vibrators with a metallic 
cone, covered with a layer of paraffin, which, according to 
my experiments, thoroughly resists this force, and connedt. 
the cone with wire similarly insulated. 
The force can also be obtained from a Ruhmkorff’s coil of 
moderate size, by drawing a knife across one of the posts 
near the end of the magnet. It does not seem to make 
much difference whether or not the outer coil be closed ; the 
force depends wholly on the primary coil. The difficulty of 
experimenting with Ruhmkorff’s coil is that, unless great 
care be exercised, indudtion-currents will be obtained. In 
all these experiments, the battery, the eledtro-magnet, or 
coil, may be thoroughly insulated, so as to exclude all possi- 
bility of currents of induction over the sides of the cells, 
and the completion of a circuit through the air. The force 
can be obtained just as well, however, even when no pains 
are taken with the insulation. In studying this force the 
dark box is almost indispensable. A small box of any kind 
from which the light is excluded, except through a hole at 
the top, will answer. The pencil points should be carefully 
sharpened, and should meet in the dark box just beneath the 
hole in the top. 
These pencil points should be made to approach and 
recede from each other, a distance about equal to the thick- 
ness of tissue paper, a number of times, when very weak 
sparks are to be detected, but when the sparks are strong 
they may be adjusted to be almost in contadt, the fine parti- 
cles of carbon forming a chain from one pencil to the other. 
In careful experimenting when the force is passing, or trying 
to pass, through great resistance, it may be necessary to 
watch for the spark a number of minutes, varying all the 
while the adjustment of the pencil points. On the gas-pipe, 
or stove, or rusty iron of any kind, the spark can be obtained 
so as to be seen in daylight, provided it be somewhat 
shaded ; on smooth metal it is difficult to get the spark. 
Causes of Failure in Attempting to Obtain the Force . 
Those who attempt these experiments for the first time 
may fail to see the spark from any of the following causes : — 
