Part 18 (2/2)

”Well, then,” I continued, ”you see that we shall have no difficulty as to the dam. Then, as to the wheel, it will be a simple one of not more than four feet diameter, presented vertically to what I may term the water-spout, so that its axle, which will have a crank in it, will work the saw direct; thus, avoiding toothed wheels and cogs, we shall avoid friction, and, if need be, increase the speed easily, d'you see?”

”Bon, monsieur--good, good,” exclaimed Coppet, becoming quite enthusiastic in his appreciation of my plans.

”Of course,” I continued, ”the saw can easily be fitted to a frame, and a very simple contrivance can be made to drive along the larger frame that will carry the logs to be sawn; but these are trifling matters of detail which you and I will work out at our leisure, Dumont.”

”Oui, monsieur, oui,” replied the blacksmith, with tighter knitted brows, and with a readiness of a.s.sent which I do believe the good fellow would have accorded if I had proposed to fit a new axis to the world.

”There is only one thing that troubles me,” said I: ”how are we to gauge or estimate the force of our water-spout so as to regulate our mill when made? Do you understand such matters--the measurement of force-- Coppet?”

The carpenter shook his head.

”That's unfortunate. Do you, Dumont?”

”Non, Monsieur.”

”H'm! I'm sadly ignorant on the point myself,” I continued. ”Of course I know that so many cubic feet of water will exert a certain pressure, but then I don't know what that certain pressure is, nor how to find out how many cubic feet our somewhat irregular dam will contain. Nor do I know precisely the strength of the material required in the dam to resist the water.”

Dumont humbly suggested here that we could at all events act on the principle that guided Adam and Eve in the formation of their first water-mill, and find out by experiment. And Coppet said that we could get over the difficulty about the strength of materials by making everything ten times stronger than was required.

”You are right lads,” said I, much amused with the earnest manner in which they gave the advice. ”Now let us go at it without delay, so that we may get into working order before the frost stops us.”

We set to with enthusiasm, and progressed with our labour much faster than I had expected. The natural basin, to which I have referred, lay just below a ledge of rock over which the rivulet flowed into it, forming a pretty deep pool about ten feet in diameter. Flowing out of this pool, it ran about twelve feet further through a narrow gorge, where it dropped over another ledge. Now, all that we had to do was to shut up the outlet of the narrow gorge with a strong dam, and so cause the pool to swell and rise into a small but very deep pond.

Our first step was to divert the channel of the brook so as to leave us free to construct the dam. The nature of the ground rendered this easy enough. Then, before going further, we made the trough which was to conduct the water out of the dam. It was made of four strong planks about ten feet long and eight inches wide, forming, so to speak, a square pipe. This we laid firmly in the bottom of the basin with its end projecting over the lower ledge. To the inner end we attached a perpendicular piece of wooden piping which rose several feet from the ground. This was meant to prevent mud and stones from getting into, and choking, the pipe.

This done, we laid some very large timbers over the pipe and across the opening of the gorge, above and between which we put heavy stones and large quant.i.ties of gravel--also turf and twigs, and all sorts of rubbish. Thus was the dam begun, and we continued the process until we raised it to a height of some twenty feet or so.

”What a magnificent pool it will be to dive in!” said Lumley, one day, when he came to see us at work.

”Won't it,” said I; ”especially in winter!”

”Whatever happens to your works, the dam, I think, will never give way,”

continued Lumley; ”it seems to me unnecessarily strong.”

Not to try the reader's patience, I may say at once that we advanced with our labour without a hitch until it was nearly finished. To the opening in the pipe or spout we attached a powerful sluice, by which to stop the flow desired, and, all being ready, broke down the d.y.k.e that had turned aside our stream, and let the water in. Of course we had constructed an overflow part of the basin, by which to conduct the surplus water back to its proper channel below our works.

It was a trying moment when we first let the water in. Would it leak?-- would it break down?--was in everyone's mind. I had no fear as to the latter point, but felt uncertain as to the former. We had much longer to wait, however, for the filling than I had expected; but when at last it was full up to the brim, and the trees around were reflected on its surface, and no leak appeared anywhere, I could not resist giving a cheer, which was heartily taken up and echoed by our whole party--for we had all a.s.sembled to watch the result.

”Now, Coppet, lend a hand at the winch. We'll open the sluice and observe the force.”

After a few turns our winch refused to move, and only a small part of the opening had been uncovered, from which the water was squirting furiously.

”Something wrong,” said I, looking down at the men below. ”Just take a look, Salamander, and see what it is.”

Our lively interpreter went down on hands and knees and made an earnest examination, despite the squirting water.

”Oh! I sees. All right now,” he shouted, ”heave away!”

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