: STORIES FROM PHYSICS
: Fables For Children, Stories For Children, Natural Science Stori
There was once a learned Italian, Galvani. He had an electric machine,
and he showed his students what electricity was. He rubbed the glass
hard with silk with something smeared over it, and then he approached to
the glass a brass knob which was attached to the glass, and a spark flew
across from the glass to the brass knob. He explained to them that the
same kind of a spark came from sealing-wax and amber. He showed them
that feathers and bits of paper were now attracted, and now repelled, by
electricity, and explained to them the reason of it. He did all kinds of
experiments with electricity, and showed them all to his students.
Once his wife grew ill. He called a doctor and asked him how to cure
her. The doctor told him to prepare a frog soup for her. Galvani gave
order to have edible frogs caught. They caught them for him, killed
them, and left them on his table.
Before the cook came after the frogs, Galvani kept on showing the
electric machine to his students, and sending sparks through it.
Suddenly he saw the dead frogs jerk their legs on the table. He watched
them, and saw that every time when he sent a spark through the machine,
the frogs jerked their legs. Galvani collected more frogs, and began to
experiment with them. And every time he sent a spark through the
machine, the dead frogs moved their legs as though they were alive.
It occurred to Galvani that live frogs moved their legs because
electricity passed through them. Galvani knew that there was
electricity in the air; that it was more noticeable in the amber and
glass, but that it was also in the air, and that thunder and lightning
came from the electricity in the air.
So he tried to discover whether the dead frogs would not move their legs
from the electricity in the air. For this purpose he took the frogs,
skinned them, chopped off their heads, and hung them on brass hooks on
the roof, beneath an iron gutter. He thought that as soon as there
should be a storm, and the air should be filled with electricity, it
would pass by the brass rod to the frogs, and they would begin to move.
But the storm passed several times, and the frogs did not move. Galvani
was just taking them down, and as he did so a frog's leg touched the
iron gutter, and it jerked. Galvani took down the frogs and made the
following experiment: he tied to the brass hook an iron wire, and
touched the leg with the wire, and it jerked.
So Galvani decided that the animals lived because there was electricity
in them, and that the electricity jumped from the brain to the flesh,
and that made the animals move. Nobody had at that time tried this
matter and they did not know any better, and so they all believed
Galvani. But at that time another learned man, Volta, experimented in
his own way, and proved to everybody that Galvani was mistaken. He tried
touching the frog differently from what Galvani had done, not with a
copper hook with an iron wire, but either with a copper hook and a
copper wire, or an iron hook and an iron wire,--and the frogs did not
move. The frogs moved only when Volta touched them with an iron wire
that was connected with a copper wire.
Volta thought that the electricity was not in the dead frog but in the
iron and copper. He experimented and found it to be so: whenever he
brought together the iron and the copper, there was electricity; and
this electricity made the dead frogs jerk their legs. Volta tried to
produce electricity differently from what it had been produced before.
Before that they used to get electricity by rubbing glass or
sealing-wax. But Volta got electricity by uniting iron and copper. He
tried to connect iron and copper and other metals, and by the mere
combination of metals, silver, platinum, zinc, lead, iron, he produced
After Volta they tried to increase electricity by pouring all kinds of
liquids--water and acids--between the metals. These liquids made the
electricity more powerful, so that it was no longer necessary, as
before, to rub in order to produce it; it is enough to put pieces of
several metals in a bowl and fill it with a liquid, and there will be
electricity in that bowl, and the sparks will come from the wires.
When this kind of electricity was discovered, people began to apply it:
they invented a way of gold and silver plating by means of electricity,
and electric light, and a way to transmit signs from place to place over
a long distance by means of electricity.
For this purpose pieces of different metals are placed in jars, and
liquids are poured into them. Electricity is collected in these jars,
and is transferred by means of wires to the place where it is wanted,
and from that place the wire is put into the ground. The electricity
runs through the ground back to the jars, and rises from the earth by
means of the other wire; thus the electricity keeps going around and
around, as in a ring,--from the wire into the ground, and along the
ground, and up the wire, and again through the earth. Electricity can
travel in either direction, just as one wants to send it: it can first
go along the wire and return through the earth, or first go through the
earth, and then return through the wire. Above the wire, in the place
where the signs are given, there is attached a magnetic hand, and that
hand turns in one direction, when the electricity is allowed to pass
through the wire and back through the earth, and in another direction,
when the electricity is sent through the earth and back through the
wire. Along this hand there are certain signs, and by means of these
signs they write from one place to another on the telegraph.