and scratches or writes upon it. Thus a record is made of a dictated letter, a speech or a song. When the cylinder is put into the machine and the needle made to move over the same marks the sounds recorded on the roll are repeated. The sounds are magnified in a trumpet, and so made loud enough to be heard by our ears. On a phonograph record-roll you can see the faint, irregular line made by the needle. A given sound always makes the same kind of mark. Of course, then, it must always give back the same sound.
HOW DOES SOAP TAKE OUT DIRT?
You can find out the answer to this by making a little soap in a greasy frying pan. Put a very little water and a big spoon full of washing (lump) soda in it, and let them boil together. You get a thick soft soap. The grease is broken up and mixed with the soda, and the frying pan is cleaned. Our grandmothers made great kettles full of soft, brown soap by boiling waste fat and wood ashes lye together. Lye, soda and potash, or what are called the alkalies, break up and dissolve the fats. Our skin makes a kind of oil all the time. This oil gathers dust, and makes us and our clothing dirty. We can cut this dusty oil from the skin with soda or some other alkali, dissolved in water. But an alkali is so strong it dries out and breaks up the skin as well as the oil. So we weaken the alkali with other oils or fats first. There is still an excess of alkali in the soap called "free" alkali, enough to take up the oil in our skins and clothing without injuring them. Of course, with the oil comes the dust. If your face smarts or shines after a scrubbing with soap, it is probably because the kind of soap you use has too much "free" alkali in it for your skin. Or the water is hard and does not dissolve the soap properly. As waters and surfaces to be cleaned differ so much, many kinds of soap are necessary.
WHAT IS THE HORIZON?
The horizon is the boundary of as much of the world as you can see from the place in which you happen to be standing. If you are on the ocean, or on a flat plain with no houses or trees to break the line, the horizon is a perfect circle, because you are able to see the same distance in every direction. The horizon, then, is the circular line where the earth and sky seem to meet. The distance that can be swept by the human eye, depends upon the height from
