Page:Popular Science Monthly Volume 92.djvu/182

 166 Popular Science Monthly

Wliy Monkeys Use Their Fists Explosives Are Simpler in Com-

��Instead of Their Hands

WHEN next you go to the zoo, watch the monkeys use their hands. Notice how they seize things with their fists. They do not use their finger-ends as we do. While the higher monkeys, such as gorillas and chimpanzees may be taught to use their fingers, they never learn to use them as easily as do human beings.

The monkey is primarily a tree- dweller. It lives in forests and swings from tree to tree, using its hands as hooks with which it grasps the branches. The thumb is not brought into play. Some South Amer- ican monkeys have lost the thumb through disuse; all that is left of it is indicated by a little lump under the skin.

In the higher monkeys the wrist is built like yours. It has the same number of bones. But the monkey has never used his wrist, and so it has lost the flexibility. The monkey can use its feet to better advantage than its hands.

Man, on the other hand, has used his feet so long simply for the purpose of walking, that he would experi- ence considerable difficulty in using them as he uses his hands. Yet, it is amazing how quickly a man can learn to use his toes as he does his fingers. If you don't believe this, just try to write with your toes. At first the letters will be very large and awkward. But with a little practice you will find that- you can write with your foot more easily than with your left hand, if you are naturally right- handed. It is an attractive exercise with which to while away an hour. We know you will try the experiment.

���An educated chimpanzee threading a needle. His thumb is not well developed

��position than They Seem

HERE, gentlest of readers, we have an object lesson in explosives. The inventor of a particularly new and violent kind is throwing it against a tree in demonstration of the fact that it will not "go off" in the absence of the proper kind of primer. It even may be lighted with a match, and it will burn like a pitch torch — but no ex- plosion. But should you attempt to set it off with a certain primer, you will ar- rive elsewhere v/ith promptness and ex- ceeding dispatch.

Most smokeless powders will admit of similar treatment. These features about explosives seem most unusual, until one looks into the physi- cal principles back of their action. Ex- plosion is simply a burning. The quicker the burning the higher the "high" explosive. If an ob- ject burns; i. e., is converted into gas quickly, the expansion resulting is capable of exerting tremendous force on whatever happens to contain the object. Here is the force that drives projecciles such tremendous distances.

���Throwin^i this explosive against a tree will not detonate it; a special primer is necessary

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