CHEMICAL ACTION
Fig. 182. Etching copper with acid.
Fig. 183. Strong acids will eat holes like this in cloth.
Fig. 184. The lye has changed the wool cloth to a jelly.
Fig. 185. Making a glass of soda lemonade.
Fig. 186. The platinum loop used in making the borax bead test.
Fig. 188. The white powder that is forming is a silver salt.
Fig. 189. The limewater test shows that there is carbon dioxid in the air.
B. Construction of the Cigar-box Telegraph
Fig. 191. The cigar-box telegraph.
THE HERO OF THE LONGHOUSE
COMMON SCIENCE
CHAPTER ONE
GRAVITATION
Section 1. A real place where things weigh nothing and where there is no up or down.
Why is it that the oceans do not flow off the earth?
What is gravity?
What is "down," and what is "up"?
There is a place where nothing has weight; where there is no "up" or "down"; where nothing ever falls; and where, if people were there, they would float about with their heads pointing in all directions. This is not a fairy tale; every word of it is scientifically true. If we had some way of flying straight toward the sun about 160,000 miles, we should really reach this strange place.
Let us pretend that we can do it. Suppose we have built a machine that can fly far out from the earth through space (of course no one has really ever invented such a machine). And since the place is far beyond the air that surrounds the earth, let us imagine that we have fitted out the air-tight cabin of our machine with plenty of air to breathe, and with food and everything we need for living. We shall picture it something like the cabin of an ocean steamer. And let us pretend that we have just arrived at the place where things weigh nothing:
When you try to walk, you glide toward the ceiling of the cabin and do not stop before your head bumps against it. If you push on the ceiling, you float back toward the floor. But you cannot tell whether the floor is above or below, because you have no idea as to which way is up and which way is down.
As a matter of fact there is no up or down. You discover this quickly enough when you try to pour a glass of water. You do not know where to hold the glass or where to hold the pitcher. No matter how you hold them, the water will not pour—point the top of the pitcher toward the ceiling, or the floor, or the wall, it makes no difference. Finally you have to put your hand into the pitcher and pull the water out. It comes. Not a drop runs between your fingers—which way can it run, since there is no down? The big lump of water stays right on your hand. This surprises you so much that you let go of the pitcher. Never mind; the pitcher stays poised in mid-air. But how are you going to get a drink? It does not seem reasonable to try to drink a large lump of water. Yet when you hold the lump to your lips and suck it you can draw the water into your mouth, and
