saying, "Just let me hear any of you call my brother 'Cad' again."

It is pleasant to relate that this manly, gallant-spirited fellow was a capital student. He rose from class to class until he reached the highest, amongst boys two years older than himself, and in the competition for prizes was invariably successful.

CAMBRIDGE SERIES

OF

INFORMATION CARDS FOR SCHOOLS.

No. 2.

The Sun as a Worker.

BY

W. J. ROLFE, A.M.

Everybody knows that we are indebted to the sun for light and heat, but this is by no means all that we owe to him; or, rather, this includes a good deal more than we may see at first sight. The sun really does all, or nearly all, the work of the world. We talk of water-power, wind-power, steam-power, animal power, and the like; but all these are only kinds of sun-power. Let us look at them one by one, and see if the sunbeams are not the forces within or behind them all.

Water-power is the force exerted by falling or running water; and running water is falling water. In the most familiar forms of water-wheels, troughs—or buckets, as they are called—are arranged on the rim in such a way that the water runs into those on one side of the wheel near the top, making that side heavier, so that it descends. As the buckets go down, the water runs out of them, but those above are being filled in their turn, so that this side of the wheel is continually weighted with water, while on the other side empty buckets are going up. The wheel may turn mill-stones to grind wheat or corn, or may give motion to machinery for spinning and weaving cotton or wool; but is it the water-wheel that really does the work? "No," you will say; "if we trace back the force that moves the machinery, we find it in the falling water that fills the buckets of the wheel; it is the water-fall that is the real worker." No; it is the sun, which is a force behind the water-fall, as the water-fall is the force behind the wheel. What supplies the water-fall with its never-failing stream? The rain that fills the springs high up among the hills, where a little brook has its source—the rain that feeds the brook as it flows, and other brooks that join it on its way, until it becomes the river that descends in the water-fall. And what is the source of the rain? The sun, whose rays turn the waters of the earth to vapor, and lift them up to the clouds, whence they fall upon the hills. Were it not for the sun the rain would soon cease to fall, the springs in the hills would dry up, the brooks would run out, the river would dwindle away, the roar of the water-fall would die into silence, and the wheel would stop for want of power.

The wind, which is the motive force of windmills and of sailing vessels, is another form of sun-power. The atmosphere has been compared to a great wheel carried round by the heat of the sun. We know that when air is heated it rises, and that the tropical parts of the earth are hotter than the polar regions. In the tropics, therefore, the heated air rises, and the colder air from the poles flows in to fill its place, while the place of the latter is filled by an upper current flowing back from the equator; and this goes on continually, and keeps the great atmospheric wheel turning. Wherever a wind blows, the process is similar: it is the sun that causes the wind, be it zephyr, or gale, or hurricane.

"But," you will say, "the sun does not run our steam-engines; it is artificial heat, not natural heat, that changes the water into steam." Very true; but how do we get this heat? By burning wood or coal. For the former we are clearly in debt to the sun, which made the trees grow that furnish the fuel; and the coal is the remains of plants that grew long before the creation of man, plants that were as dependent on the sunshine as those that flourish to-day. When we burn coal, the heat we get from it is nothing but the sunbeams that were caught and imprisoned by those ancient plants; our steam-engines use the force that was stored up by the sun millions of years before the steam-engine was invented.

All muscular power, whether of man or of other animals, may be traced to the same source. Animals get their food either from plants or from other animals that have fed upon plants; and the plants owe their existence to the sun. The animal is a machine, like the steam-engine; the food which it eats is the fuel that keeps the machine in action. With every movement we make, a portion of this fuel is burned up in our muscles. Every beat of our hearts is at the expense of such material; and the material is the gift of the sun. Our very thoughts are indirectly dependent on the sunbeams; for the brain, which is the organ of thought, requires food to maintain its activity, like the muscles and all the other machinery of the body.

There are other kinds of force less familiar than these—as electricity, magnetism, and chemical force—which can also be proved to come indirectly from the sun, but the proof can not be given here. We can detect the work of the sunbeams in the flash of the lightning and the roar of the thunder, in the turning of the compass-needle to the north, and in all the wonders of chemical science, as certainly as in the growing plant or the running stream.

The only form of force known to us which does not come entirely from the sun is that of the tides. The tidal wave is raised and carried round the earth mainly by the attraction of the moon. The sun, though immensely larger than the moon, is so much farther off that it attracts the waters of the earth much less than the moon does. A tide-mill, which gets its motive power from the rise and fall of the tide, is therefore worked by the moon rather than by the sun.

[By special arrangement with the author, the cards contributed to this useful series, by W. J. Rolfe, A.M., formerly Head-Master of the Cambridge High School, will, for the present, first appear in Harper's Young People.]

HARRY SWIMS FOR THE EDDY.

THE MORAL PIRATES.

BY WM. L. ALDEN.

Chapter III.

As Harry vanished, Joe's head appeared, as he climbed up the side of the bridge and joined his brother and Tom. Their anxiety was now for Harry, who had been swept through the channel under the bridge, and was manfully swimming toward the eddy where the boys had landed. He came ashore none the worse for his bath, and was delighted to find that Joe was not only safe, but dry. Joe explained that the boat had drifted against one of the piles of the bridge, and the current and the tow-rope together had forced one of her sides so low down that the water began to pour in. Joe thought that if the river intended to get into the boat, he had better get out; so he sprung up and caught one of the timbers of the bridge, and so climbed safely up to the roadway. The boat, relieved of his weight and freed from the tow-line, drifted quietly away, and was now floating peacefully on the river about twenty rods from the shore.

Luckily an old man in a row-boat saw the run-away Whitewing, and kindly caught her and brought her up to the bridge. As the boys baled her out, they told him how the accident happened, and the gruff old man said it "sarved 'em right." "When you tow a boat next time," he continued, "you'll know enough to put all your weight in the stern. Did you ever see a steam-boat towing a row-boat with a man in the bow? If ever you do, you'll see him go