Then came his bad luck.

He was tossing his ball upon the roof of the house, and catching it as
it came down; but by and by it did not come down--it bounded into the
tin eave-trough and rolled slowly along till it came to the big pipe
that led to the cistern, and into this it dropped, and went whirring
down, and stopped somewhere with a faint plash.

For once in his life, Johnny felt as if the world had slipped from
under him.

For a few minutes he was bewildered; then came the joyful assurance
that his Steele would help him out of his trouble, and if Steele
couldn't, there was the schoolmaster.

The first thing he did was to lift the cover off the cistern, though
he knew well enough the ball was in the pipe, as he well remembered
that it ran nearly to the bottom of the cistern and then made a sharp
bend upward, "so that the water mightn't wear the cement," the mason
told him.

He found the water quite low, but not low enough to show the mouth of
the pipe. Of course, there was no ball in sight. He closed the cistern
with a groan, and got out his new book on natural philosophy. First he
glanced at optics; but that did not help him to see his way; then at
hydrostatics and hydraulics.

It was of no use; nothing seemed to hit the case. Then he gave it up,
put his book away, and went to consult the school-master. Johnny found
him among his books, and told him all about it.

"Have you tried to fish it out with a hook and line?"

Johnny's face brightened. "No, sir, I never thought of that."

"All right; you couldn't do it. Besides, if you could, it wouldn't be
scientific," said the school-master. "Now, go home, take a ten-foot
pole, and measure the distance from the eaves to the water in the
cistern, then find the diameter of the pipe, and on my way to school
to-morrow morning I will tell you the three things necessary for
recovering your ball."

Johnny fairly flew home, got a pole, measured the distance from eaves
to water and found it to be twelve feet; measured the pipe and found it
to be two inches and one-half. Then he put away the pole, did his
chores, ate a hearty supper, and went to bed.

He was up bright and early next morning, and got quickly through his
chores, so that when the school-master stopped, on his way to school,
he was ready to see about the ball.

"Good morning, Johnny! Glad to see you on hand. How long's the pipe?"

"Twelve feet, sir."

"Diameter?"

"Two inches and a half, sir."

"A