“It’s the most common method of measuring water for irrigation purposes. I’ve been making an apparatus to measure the water flow, and I can show you by working it better than by explaining. But just let me finish this grader first.”
As Andy had found the grade to be 1 inch per rod, he cut the third board to a length of 8 feet and 5 inches, then nailed it firmly to one end of a long board, and the 8-foot 4-inch piece to the other. This done, he put a strip of 1-inch board under the shorter leg, then bound a carpenter’s spirit level to the centre of the long board.
“You carry this carefully, Ted,” he ordered, giving the home-made grader to the boy. “I’ll get my measuring board, and then we’ll go back to where we are intending to put in the dam.”
Interestedly the young homesteaders inspected the latter piece of apparatus after they had reached the site of the reservoir. It consisted of a board 1 inch thick, 12 inches wide, and 8 feet long. In this had been cut an opening 50 inches long and 6 inches wide, the centre of the slot, on the upstream side, being 4 inches from the top of the board, while the down-stream side was bevelled to present a sharp edge to the water.
A second 12-inch board, with one end fashioned into a handle, was placed against the upstream side of the slot and so hung upon the first board that it could be shoved back and forth. On the down-stream side of the opening, a bevelled block was fitted and screwed to the second board, and the inches were marked.
Placing the apparatus in the creek so that it dammed it, the water quickly flowed over the top.
“Pull that handle back until the block is at the 12-inch mark along the slot,” directed Andy. As Phil did so, the water fell below the top of the board.
“Now shove it back until the water is level with the top,” the agent ordered. And when it had been done, Ted said the block was at the 6-inch mark.
“The number of miner’s inches flowing through the slot is equal to the total square inches in the opening, that is, near enough for all practical purposes in a small stream like this,” explained Andy.
“Why, that makes 36 miner’s inches,” said Phil. “What was the use of doing all this when the table showed 37 miner’s inches, with a 6-inch head, for a grade of 1 inch per rod?”