[Illustration:  Fig. 257.  A Paddle.]

[Illustration:  Fig. 258.  How the Paddles and Cans Were Attached.]

The Receiving Trough.

Our next task was to nail the receiving trough in place on the higher tower.  We set up the towers on land and mounted the wheel between them with the axle resting in the crotch of the short tower and in a deep notch cut in the cross boards of the larger one.  The cans on the wheel faced the larger tower, but the hub at the center and a block nailed to the larger tower spaced the wheel far enough out so that the cans did not strike the tower as they revolved.  We carefully measured the distance between the spokes and the larger tower, and then built a square trough of a size to just fit into this space.  This trough was nailed across the end of the V-shaped trough on top of the tower, but a notch was cut in the side so that the water would pour from the square or receiving trough into this V-shaped one.  The square trough was about 8 feet long and its sides were 12 inches high; but at the ends we had to cut them down to a height of but 6 inches, so as to permit the cans to pass without hitting them.

[Illustration:  Fig. 259.  The Receiving Trough.]

Setting Up the Towers.

Our filter was located nearly 20 feet from the end of the river, and in order to get a good current of water to revolve our wheel we had to place it about 15 feet from shore.  This necessitated building a trough line 35 feet long.  Ten feet of this line were already provided in the top of the tall tower.  This tower was now set up in place with the legs firmly wedged into holes excavated in the bottom of the river.  The legs on the shore side were sunk a little deeper, so as to tilt the trough slightly shoreward.  The outer end of the trough was about 12 feet above the level of the water.  We needed but one more tower to support the remainder of the trough line.  This tower was built like the first one, but was much shorter, as it was erected on land and the level of the trough at the top had to be 5 or 6 inches lower so as to make the water flow.  We connected the towers by another V-shaped trough section.  This we nailed to the under side of the first trough and to the inside of the second trough.  The latter was then in the same way connected by a trough section with the upper filter barrel.  We now rigged up our shorter tower about a foot from the taller one, wedging in the legs so that the top came level with the slotted boards of the other tower.

Mounting the Water Wheel.

Then came the task of mounting our wheel in place.  We were working in a pretty strong current and found it no easy matter.  In the first place, the wheel was floated down to the towers, but there it got jammed and we couldn’t lift it up.  One of the paddles was broken and a bucket wrenched off before we could disentangle the wheel from the towers, and then the wheel was carried quite a distance down-stream before we could drag it in to shore.