Harper's Young People, June 15, 1880

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.]

[Illustration: HARRY SWIMS FOR THE EDDY.]

THE MORAL PIRATES.

BY WM. L. ALDEN.

CHAPTER III.

As Harry vanished, Joe's hea