15. Description of Mr. Smeaton's Hand-Pump for Ships.
This pump was invented by Mr. Smeaton in 1765, and was intended to remedy a defect in all pumps used at sea. As the common ship's pumps deliver the water on the main deck, about 4, 5, or 6 feet above the surface of the sea, a quantity of power is thus unnecessarily expended. To remedy this evil, Mr. Smeaton employed horizontal wooden trunks or pipes, which carried off the water through the ship's sides at as low a level as possible. One end of these pipes proceeded from the upright trunk of the pump, and the other was fitted into boxes, or short wooden tubes, let in through the ship's side, and caulked just above the load water line. " These side pipes were closely juinted with the boxes in the ship's side at one end, and at the other end into strong planks, which were bolted against the sides of the pump, in order that the side pipes might be got out and in without disturbing the pump, which was a sucking pump with its bucket worked by a lever or brake upon the deck over the pump. From the top of the pump, a stand pipe was carried up to the main deck, or as high as was thought necessary to prevent the water reverting and running back into the ship, over the top of the pump, when the sea rose above the orifices of the side pipe, or when from the ship being in distress, they were under her load water line. By this, even when both boxes and pipes were wholly under water, it would no ways interrupt the action of the pump, for whenever the water in the stand-pipe rose above the level of the water without, the pressure of the column in the stand pipe, would cause it to make its way through the side pipes, so that in this case no level way lost ; and though the pump was at rest, no water collie revert down the pump; because there were the valves o! both bucket and fixed box or clack, which prevented it The working barrel was of brass, and very truly bored, the bucket and fixed box being of the same construction a! those used in the steam-engines, and the pump rod wag made of greater bulk than was necessary, merely fen strength, but by way of weight, that, when the brake wai 71-1 _ _ V t T V T lifted up, the pump rod should readily descend by its own weight. The brake of the putnp had a branch fixed on,
rather obliquely at each side, so as to form three handles. for four men to work at once ; they stood one on each side the middle stem of the brake, and one on the outside of each of tl.c branches ; and every quarter of an hour they could relieve themselves by changing hands, which was done by changing places. They were intended to make no more than twenty-five strokes per minute, move the pump rod 171. inches up and down at each stroke, the barrel being a nine-inch bore. This was much better than making shorter strokes, and quicker, as they usually do. Their hands moved up and down about four feet six inches, and by working with this stroke at a moderate rate, so as to hold it an hour, four men would in that time deliver 20 tons, at a height of 22 feet. This was upon a supposition of raising the water, to the usual height ; but when, by the application of the maxims, before described, this perpen dicular was shortened to 16 or 17 feet, then nearly the same delivery could be made by three men, or proportion ably more by four men ; that is, as 17 : 22 : : 20 : 26 tons, at 17 feet. The foot of the pump was let through the ship's inner planking or ceiling, betwixt two of the floor timbers, and did not touch the bottom or outside planking within 21 inches, the lower end being rounded within side like a trumpet mouth, it being a bad plan to have the pump standing upon its lower extremity, with holes bored to let in the water, as it is thus very liable to be choked by dirt. A plank of the ceiling was made to lift up neat' the pump's foot, that a man could occasionally get in his arm, to clear away any chips, sand, or dirt, or other mat ter that should happen to be drawn thither." 16. .9ccount of Mr. TVitty's Inzprovcment on Pumps.