Part 41

How Birds Are Taught to Fly.

The next step brings us to the birds. Before they can look after themselves the little birds must learn how to search for food and the kinds of food good for them. They have to learn the habits of their kind of life. The higher you go in the study of animal life the greater seem to be the dangers which surround the young animals and the longer it takes to teach them how to look after themselves and what to do for themselves.

The bird family includes not only the robins, larks, sparrows and pigeons, but also the ducks, geese, and chickens, etc. We are all more or less familiar with birds’ eggs, and if not we know what a hen’s egg looks like. The eggs of the bird family are laid in nests, which is the first sign of home building in the animal kingdom.

The birds are the first of the large class of warm-blooded animals. The egg here represents again the reproductive power. The eggs, too, form in the body of the female bird, but are laid in a nest which the parent birds build together. Now this is the first step away from the fish family. The fish looks for a suitable place to lay the eggs and then goes off and leaves them. The birds, however, have to make a nest in which to deposit the eggs. The fish, as you remember, depended upon the warm sun shining on the shallow water to hatch out the eggs, thus depending on an outside force to supply the necessary warmth. In the bird family the mother bird must cover the eggs with her own body and keep them warm until they hatch out. Then, too, the father and mother birds feed the young until they are strong enough to fly and find food for themselves, and so the mother and father birds look after their babies until they are old enough to look after themselves. When this time arrives the old birds cease to bother about the young ones altogether. The fishes never act like parents after the baby fishes are born, because the little fish are able to look after themselves right away. The parent birds are a good deal like fathers and mothers for a time, but only so long as it takes them to teach their little bird children to look out for themselves. Then they forget the children completely.

It requires but a few days and no parental care to hatch out a family of baby fishes and no attention at all after birth. It requires several weeks and much patience for the parent birds to hatch out their eggs, and it involves care and attention for several weeks to teach baby birds to take care of themselves.

This being a father or mother in the animal kingdom becomes a greater responsibility in every step as we get closer to man, and when we reach man we find him to be the most helpless offspring of all at birth, and that it takes more time, care and attention to bring up a human child to maturity than any other animal.

What Makes the Hollow Place at One End of a Boiled Egg?

This hollow place on the end of the boiled egg (sometimes it shows on the side) is the air which is put inside of the egg when it is formed so that the little chicken will have air to breathe from the time it comes to life within the egg until it becomes strong enough to break the shell and go out into the world. There is also food in the egg for him. When you boil the egg this pocket of air within the shell, which would have been used up by the chick if the egg had been set to hatch instead of being cooked for breakfast, begins to fight for its space and pushes the boiling egg back and forms the hollow place.

The purpose of the air in the egg is a good thing to remember when we come to study the higher forms of animal life from the standpoint of how they reproduce themselves.

The mammals are the next higher form of animals. The babies of this class of animals must be fed for several weeks or months before they are ready to come into the world.

A little chicken is ready to come out of the egg almost as soon as it comes to life, and, therefore, needs only a little air and food before it is strong enough to peck its way out, but the babies of mammals begin to live months before they are ready to come into the world, and they need a great deal of air and food during this time. This class includes the dogs, horses, cows, cats and all other animals in the Zoo and in the woods. The name mammals means the same as “mamma,” and indicates an animal which must be fed from the body of a female mammal even after it is born.

In this class the eggs are retained within the body of the female animal instead of being laid in a nest or some other place, as in animals of lower classes, after being fertilized by the male animal, so that the baby animal may secure its food and air from within the mother’s body after the life within the egg is begun.

The mother’s body supplies the necessary warmth to develop the life of the little animal in the egg, just as the birds supplied this with their bodies. In the bird class it only takes a few hours to give the little bird sufficient strength to peek his way out, but in the mammal class it is a long time before the baby animal is strong enough to come out into the world, and even after it is born the babies of mammals require a great deal of care and attention before they are able to look out for themselves. During this period the animal secures all of its food from the breast of the mother animal.

Another reason why the eggs of mammals are retained within the bodies of the females is the need for protecting the young animals from enemies. In the animal kingdom each kind of animal preys upon another kind. They attack and devour each other and are constantly in danger. If, then, mammals laid eggs in nests and sat upon them to hatch them out, the mother animals sitting on the nests would be continually in danger of attack from their enemies. They would either have to flee and subject the nest and its contents to the danger of destruction or else stay and fight, and perhaps be destroyed. But by carrying her egg within her body the mother mammal is able to move about from place to place and protect her baby.

Is Man an Animal?

Men, women and children belong to the “mammal” class of animals. The offspring of the human family is the most helpless of all animals at birth. The young of most kinds of mammals can stand on their legs shortly after being born, but the human baby requires months before it can stand up. A baby horse can also walk within a few hours, but human children do not begin to walk until they are more than a year old.

Why Cannot Babies Walk as Soon as Born?

The human baby has a great many more things to learn than a horse baby before it is safe for him to go about alone. It takes time for the brain to develop, and if a baby could walk before the brain had even partially developed it would only get into trouble.

This, then, is what we have learned about the reproduction of life and the reasons for its being different in different classes of life. First, we had the division of organic life into the vegetable and animal kingdoms. Life in the vegetable kingdom has none of the five senses, for plants cannot see, hear, feel, smell or taste. They cannot move from place to place, but remain where they grow until destroyed or removed. On the other hand, all animal life has at least one of the five senses--feeling. The oysters and clams belong to this class. Starting with this level of life in the animal kingdom we find that as we go on up through the different classes we find each class able to do things which make it superior to the class below it, until we reach the human mammal, who can do most of all. And, further, that since each class as we go up in the scale of life has greater ability to do things than the class beneath it, so in each case the task of the parents in preparing their offspring for their kind of life becomes greater, and the period during which the offspring is learning becomes longer and longer until we reach the human family, in which we find that parents have the greatest responsibility, and the children are the most helpless of all animals, but that in the final result man has a right, on account of his superior qualities, to be the ruler of the other creatures of the world.

What Are Ball Bearings?

Some years ago a gentleman in trying to find some way to reduce the friction, which is constantly developed to a certain extent, even when the axle is oiled, discovered that if between the axle and the inside of the hub a circle of steel balls were arranged, so that the hub of the wheel did not touch the axle at all, but rested on the little balls which in their turn touched the axle, that a great deal of the friction was eliminated. This proved to be a wonderful invention, and when this combination is arranged and oiled, there is hardly any friction.

Why a Gasoline Engine Goes

As you know, gasoline is a very inflammable fluid, and will explode if placed too close to fire.

This explosive quality is the basic principle of the gasoline engine. By admitting a small quantity of gasoline vapor into an enclosed cylinder, and exploding it by means of an electric spark, repeating this operation continuously, the engine is given a regular rotary motion.

Look at Fig. 1. Starting from the gasoline tank, the fluid is fed into the ‘carburetor’, which is a sort of atomizer. Here the gasoline is mixed with air, and broken up into a very fine spray, in which condition it will explode readily.

The engine will not start of itself. Its fly-wheel must first be turned by hand, or by some other outside force, until the first explosion takes place. After this its action is automatic.

As shown in Fig. 1, the fly-wheel is being turned, and is drawing the piston down the cylinder, which in turn sucks gasoline vapor, (shown by little arrows) through the ‘intake valve’. This ‘intake valve’, and the ‘exhaust valve’ on the opposite side of the cylinder, are opened and closed at the proper time through the action of the gears shown in the illustration.

Passing to Fig. 2, the fly-wheel in turning has drawn the piston to its lowest point, and is now shown forcing it up the cylinder. This compresses the gasoline vapor in the cylinder to a density at which its explosion produces the greatest amount of power. The intake and exhaust valves are both closed.