“And now,” said Mr. Davy, “to get the water into the pond. Patrick and Michael must build a dam a little way up the creek and the race-way from a point just above. We shall need a gate similar to the one at the outlet.”
The boys were glad to give way to Patrick and Michael, when it came to building dams and race-ways. In the mean time they assisted the mason who was lining the embankment on either side the gate with stone, to protect it against the action of the water. The stone-boat, a little, flat vehicle which slides over the ground without wheels, was brought out, for piles of stone were to be drawn from a distant part of the farm.
“But I shall want one of you to carry the hod for me,” said the mason.
It was arranged that they should take turns at this; so one would stay and fill with mortar the queer little box which hod-carriers use, and bear it on his shoulders to the mason, who was fast laying the curved wall.
“Why do you have the wall laid in this rounding shape, papa?” asked George. “Why not have it straight?”
“Because the curve makes it stronger to resist the force of the water. You notice that the mason chooses stones which are larger at one end than at the other. He lays them so that the larger ends form the outer side of the curve—the smaller form the inner or shorter side, as you see by looking at this wall. The stones, thus wedged against each other, could not be as easily forced out of place as if they were square in shape, and laid in a straight line. Imagine the water pressing upon the inner side of the curve. How readily the wall would give way, and the water come pouring through! Have you never observed, children,” continued Mr. Davy, “that in bridges, culverts, or any structure which is to sustain a heavy weight, the foundations are always laid in the form of an arch?”
“Yes, papa,” answered George; “but I never knew why it was. I see now that it is to make them strong.”
The boys had quite enough of hod-carrying and stone-quarrying before the wall was done. In fact, Patrick was pressed into the service repeatedly. The hod became too uneasy a burden for the boys’ shoulders, even though it was padded with sheep-skin.
A channel to convey the water from the pond was now the only thing wanting. This was speedily begun, and the little workmen found themselves down in a trench behind a low rampart of earth.
“Let’s play we are soldiers,” said George. “We’ll have Patrick and Michael for captain and lieutenant (only they must work, if they are officers), and papa for general and engineer.”