The prison mirror. [volume] (Stillwater, Minn.) 1887-1894, 1890-06-19

also That such substances as metal. stone,
liquid, etc., might be attracted by the load
stone, the properties of which he had dis
covered at some length.
This science is indebted to Otto Won
Guericke for its first electric machine, con-
structed about 1870; though simple it
was great achievement at that time. 1t
was made by taking spheral glass OF or
inches diameter and placing small pieces
of sulphur within, allowing it to melt so as
to form ball, then breaking the glass,
after allowing it to cool, boring a hole
through the center and placing therein an
iron rod as an axis, then placing it on a
stand and connecting it by means of an end
less band to a large wheel turned by a
crank, it was ready for use. From this ma
chine the first electric sparks were drawn.
At the beginning of the seventeenth cent
ury one HawkSbee constructed much
more powerful machine by means of two
glass cylinders one within the other, and
constructed so that each could rotate sepa-
rately or together. He noticed also that
when exhausted the cylinders gave forth a
luminous appearance whenever friction was
applied to the surface of the cylinders. He
found also that large glass tube attracted
light bodies when rubbed with the hard.
The next experimenter with electricity
was Stephen Gray, (1695-1736). He placed
all electrical substances in two classes,
CHASING the substances that produced elec-
tricity by friction as idioelectrics. Such
| substances were glass, amber, alum, jet.
The second class contained those substances
that showed no signs of electricity when
friction was applied. Such were metals,
stones, liquids, jet; these he called anelec-
tries. Gray used as means of obtaining
electricity glass tube 31aft long and 1%in.
diameter, closing the ends with two
corks to prevent dust from settling within
the tube. The following experiment as
made by Gray led to the telegraph and
should be remembered for that alone. He
discovered while experimenting with the
tube that bodies were attracted to the cOrks
inserted in the ends of the tube; replacing
these with rods four inches long with all
ivory bell attached to the end he obtained
the same effect as before with the cork. He
kept increasing the length of the rods with
the same effect until he had 80 feet of rod
attached to the tube-with ball of cork at
the end the attraction was the same. Gray
finding this form of experiment inconven-
lent from the great length of rod used, he
resOrted to the use of pack thread. Desir-
ing to see what distance the attraction could
be carried horizontally by this means, he
suspended the thread by other pieces of
pack thread fastened to beam above, but
finding in this case no attraction what
ever, he concluded that it had travelled
horizontally until meeting with the perpen-
dicular thread which it followed until it
came to the beam. The next day telling a
friend, one Wheeler, of his experiments
Wheeler suggested going to his house and
making the experiment from one of the par
apets to the ground, some 30 feet and there
the experiment worked satisfactorily. Then
Wheeler suggested that they use silk thread
to support the pack thread while running
the experiment horizontally, and on July Q,
1929. it was carried out successfully with a
thread LAT feet in length. He tried the ex-
pertinent by using fine iron wire in place of
the silk thread, but discovered that the cur
rent was carried off by the wire. This in
brief is the discovery which led to the in
vention of the telegraph, of which 1 will
speak further on.
The next experimenter to step upon the
stage of electrical SCIENCE was a French
man, Du Fay, (169S 1887 who propOunded
theory which has not been superseded
even at the present day. His theory was
that there are two kinds of electricity,
which he calls the vitreOus and the resinous,
and that when two bodies are charged with
electricity of the same kind they repel each
other. but charged with different electrici-
ties they attract each other. If you wish to
demonstrate this to your own satisfaction
by simple experiment, take a fiber of
white silk, as cOlOred silks draw off the cur
rent, attach this fiber of white silk to the
center of straw. at each end of the straw
attach circular piece of thin paper about
one fourth of an inch in diameter. and hang
it from some fixed support; then take first,
piece of sealing wax, amber, ebonite pa
per knife, or some such article; second, a
piece OF glass tube. or tumbler dry and
warm; third. dry warm silk handkerchief.
Now rub the glass briskly with the hand
kerchief. Immediately present to one of the