The Pump Valves.

We plugged the bottom of the leader pipe with a block of wood, in the center of which a large hole was drilled.  The hole was covered with a piece of leather nailed at one side, so that it could lift up to let water into the pipe.  The piston was made of a disk of wood of slightly smaller diameter than the inside of the pipe, and over it was fastened a piece of leather just large enough to fit snugly against the walls of the pipe.  This piston was fastened to a wooden rod long enough to reach from well within the pipe to the wind wheel shaft.  A strip of brass was bent over the crank, or U-shaped bend in the shaft, and its ends were fastened to the rod.

[Illustration:  Fig. 291.  The Box Pipe.]

[Illustration:  Fig. 292.  The Lower Valve.]

[Illustration:  Fig. 293.  The Piston Valve.]

[Illustration:  The Old Windmill at Work on a Lumberville Farm.]

[Illustration:  Fig. 294.  Connection of Rod and Crank.]

Action of the Pump.

It was rather a crude pump, but it did all the work we required of it.  As the wheel went around the crank shaft would move the piston up and down.  Whenever the piston went down, the air in the pipe would press up the edges of the leather disk and squeeze past (see Fig. 295).  Then when the piston came up again, the leather disk, being backed by the wooden disk beneath it, was kept flat, so that no air could force its way back into the pipe.  This made a partial vacuum in the pipe, and the water from the well rushed up through the valve at the bottom to fill it (see Fig. 296).  When next the piston went down the bottom valve closed and more air forced its way past the piston.  Then on the next upward stroke more water flowed into the pipe, until, after a number of strokes, all the air was pumped out and the water which took its place began to force its way up past the piston and eventually to flow out of the spout into the cask.

Our old windmill was sold to a farmer near Lumberville when we broke camp that fall.  We carted it over and set it up for him.  A number of years later I saw it still faithfully at work pumping water for his cattle.  The original pump had been worn out and a new one substituted, but otherwise the old windmill remained just as we had first rigged it up.

[Illustration:  Fig. 295.  Fig. 296.  Action of the Pump.]

CHAPTER XXIV.

THE GRAVITY RAILROAD.

“About all we lack now,” said Dutchy, when the windmill had been completed, “is a railroad.”

“Then suppose we build one,” was Bill’s unexpected rejoinder.

We all thought he was joking, but he wasn’t.

“I don’t mean a steam railroad,” he said, “but a gravity railroad.”

“A what?”

“A gravity railroad.  Oh, you know what that is—­a roller toboggan—­the kind they have down at Coney Island.”  And he went on to explain how we could rig up a simple roller toboggan on our island.