Chapter VII
GALVANISM
ONCE there was a learned Italian named Galvani. He had an electrical machine and he was showing his pupils what electricity was. He rubbed glass vigorously with oiled silk, and then he approached to the glass a copper knob with a glass handle, and instantly a spark leaped from the glass to the copper knob. He told them that a similar spark would be elicited by sealing-wax and am-ber. He showed how feathers and pieces of paper are sometimes attracted by electricity, sometimes repelled, and why this is. He performed many different experi-ments with electricity and showed them to his pupils.
Once it happened that his wife was taken ill. He summoned the doctor and asked him how to cure her. The doctor ordered him to have made for her a frog soup. Galvani sent out to get some edible frogs. They were caught, killed, and laid on the table.
The cook did not come to get the frogs, and Galvani went on to show his pupils his experiment with the electrical machine, and produced sparks.
Suddenly he noticed that the dead frogs lying on the table moved their legs. He began to study them and discovered that each time he elicited a spark from the electrical machine the frogs kicked.
Galvani procured some more frogs and began a series of experiments. Each time it proved that whenever he produced a spark the dead frogs acted as if they were alive. And so it occurred to Galvani that living frogs might move their legs from this cause, that electricity might pass through them.
But Galvani knew that electricity is in the atmos-phere; that while it is more noticeable in sealing-wax, amber, and glass, still it is in the air, and that thunder and lightning are produced by atmospheric electricity.
So he began to make experiments whether dead frogs would move their legs ‘under the influence of atmospheric electricity. For this purpose he took some frogs, skinned them, cut off their heads and fore paws, and attached them by copper hooks to the roof, under an iron gutter. He thought that if a thunder-shower came up and the atmosphere was full of electricity, then the electricity would be brought to the frogs through the copper wire, and they would begin to kick.
But though several thunder-showers came up, the frogs did not move. Galvani proceeded to take them down, and while he was doing so, he touched the leg of one of the frogs to the gutter and the leg kicked ! Galvani then took the frogs and began to make the following experi-ment : he attached iron wire to the copper hook and then touched the frog’s leg with the wire the leg kicked.
Here Galvani came to the conclusion that all animals are alive only because they have electricity in them, and that electricity leaps from the brain into the flesh and thus animals move.
No one had at that time gone very thoroughly into the study of this matter, and as nothing was known about it, every one put faith in Galvani’s explanation.
But about this time another scientist, Volta, began to experiment for himself, and proved conclusively that Galvani was mistaken. He tried touching the frogs, not as Galvani had done with a copper hook and an iron wire, but first with a copper hook and a copper wire and then with an iron hook and an iron wire and the frogs did not stir. They moved only when Volta touched them with an iron wire attached to copper.
So Volta came to the conclusion that the electricity was not in the dead frog, but in the iron and copper. He continued to make his tests, and this was the result : As soon as he placed iron and copper together, electri-city was produced, and the electricity caused the dead frogs to kick. Then Volta began to try how to make electricity in a different way from what had been done before. He tried putting together various metals like the iron and copper, and he reached the conclusion that only from the contact of such metals as silver, platinum, zinc, tin, iron, he could produce electric sparks.
After Volta, new methods were invented for getting a stronger current of electricity by putting the metals into various liquids, water, and acids. By the use of these liquids electricity acquired so much more energy that it was no longer necessary to rub, as had been done be-fore; all that was required was to place in a single dish pieces of different metals and pour on them the liquid, and electricity would be created and sparks would be elicited.
As soon as this kind of electricity was discovered, methods were invented for putting it to use; they could cover objects with gold and silver by means of electricity, and by means of electricity they could transmit signals from one distant place to another.
To do this, pieces of different metals are placed in glass jars, and liquids are poured over them. The electricity is produced in these jars, and this electricity is conveyed by means of a wire to any desired place, and from that place is led into the earth. The electricity in the earth runs back again to the jars and is conducted into them by means of another wire. Thus this elec-tricity keeps going in a circuit, as in a ring by the wire to the earth and back by the earth and again by the wire and again by the earth. Electricity can go in either direction, according as you may wish : it may go first by the wire and return by the earth, or go first by the earth and return by the wire.
Over the wire, in the place where the signals are given, is placed a mag-netic needle, and this needle points in one direction if the electric current comes by the wire and returns by the earth, and in the other if the electric current comes by the earth and returns by the wire. By this needle sig-nals are given, and by means of these signals telegraphic messages are sent from one place to another.
Chapter VIII
SOLAR HEAT
ON a clear, frosty day in winter, if you happen to be in a field or in the forest, and look around you and lis-ten, you see the snow everywhere, the rivers are frozen across, the dry grass sticks out from the snow, the trees stand bare; there is not a sound.
Then look in the summer : the rivers are running and murmuring; in every little pond the frogs are calling and croaking; l the birds are flying about and singing and whistling; flies and gnats are humming and buzz-ing; 2 the trees and the grass are growing and waving. Freeze a kettle of water, it grows as hard as stone. Place the frozen kettle on the fire; the ice begins to crack, to melt, to move. The water begins to tremble and to send up bubbles; then when it begins to boil, it tosses and is agitated. The same phenomenon happens all over the world by the action of heat. When there is no heat, everything is dead. When there is heat, everything lives and moves. Little heat little motion; more heat more motion; much heat much motion; great heat great motion.
Whence comes the heat to the world ?
It comes from the sun.
In winter the sun runs low, its rays do not warm the earth, and nothing stirs. The little sun begins to go higher above our heads; it begins to send its light down directly on the earth everything grows warm, and life and motion increase.
The snow begins to melt, the ice on the rivers begins to break up, the brooks come leaping down from the hills, the vapor from the waters rises into the sky and becomes clouds, and the showers fall.
What does all this ?
The sun.
Seeds are sown, the germs sprout, the roots catch hold of the soil, from the old roots new runners strike out; the trees and grasses begin to grow.
What does all this ?
The sun.
The moles and bears come out of their lairs, flies and bees grow lively, gnats abound, fishes come out from their eggs into the warmth.
What does all that ?
The sun.
In one place the air grows warm, begins to rise, and into its place flows a colder air there is a wind.
What does that ?
The sun.
The clouds come up, they roll up and they separate, then there is lightning.
What makes those flashes ?
The sun.
Herbs, grain, fruits, trees grow. Animals feed on them, human beings make their sustenance of them, and store them up for fodder and fuel against the winter; men build houses, railways, and cities.
What furnishes the material ?
The sun.
A man builds himself a house. What does he make it out of? Of lumber. The lumber is sawed out of trees, the sun made the trees grow.
You heat a stove with fuel.
What produced the fuel ?
The sun.
A man eats bread and
