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 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 overboard mighty quick. A boat'll sheer
all over creation if you tow her with a fellow in the bow. You just put
the biggest of you fellows in the stern of that there boat, and she'll
go through under the bridge just as steady as a church."

The boys gladly took the old man's advice. When the boat was baled out,
they floated the rope down again, and when it was made fast, Tom
Schuyler, who was the heaviest of the boys, offered to sit in the stern.
His weight brought the bow of the boat out of the water, and she was
towed quickly and safely through. The boys resumed their places as soon
as