- it would obviously have been better, had the patentee made the upper part of this vessel into an air-chamber, by causing the ascending-pipe last mentioned to dip nearly to the bottom of it The annexed engraving is a representation of a rump constructed by Mr. Clymer, on the plan of the ingenious Benjamin Martin; but the suction-pipe and the valves are so disposed as to retain any heavy bodies that may be raised by the pressure of the atmosphere acting upon the vacuum.
The above perspective sketch shows that the rising main leads into a spacious valve-box, in connexion with two short and wide working-barrels, left open to the atmosphere. The piston-rods are attached to a lever, vibrating on a central fulcrum which is mounted upon a standard between the two cylinders; and to this lever branching handles are united, to enable many hands to be employed in working it. The large volume of water discharged from the barrels at each stroke of the pump causes a constant powerful stream up the rising main, so that any globular substances nearly fitting it, as cannon balls, have no oppor tunity to fall down by any intermission of pressure from underneath; they con sequently get lodged in the valve-box, and are ejected by the down-stroke of the pump. When employed as an engine to discharge water to a great height or distance, an air vessel is screwed on, as represented, and the nozzle is then plugged or capped, by which the current is directed through the air vessel.
In drawing water from great depths, the weight of the pump-rods and the water together are sometimes more than can be easily accomplished by the power at command; in such cases we have occasionally observed, in country places, a very simple apparatus, similar to that represented in the following cut, employed to counterbalance the weight of the rods. In this case, the pump rod and handle is suspended to a wooden spring, of sufficient elasticity to sustain the weight of the rods, and to require a part of the man's force to depress the piston or bucket, in return for which the spring assists him in the pull upwards. Some persons would be apt to imagine that power was thus gained; but a little consideration will enable them to perceive that it is only by a different distribution of the same force that the desired effect is produced.
In Dr. Gregory's Mechanics, vol. ii. is the fol lowing description of a pump, with little friction, which may be constructed in a variety of ways by any common carpenter, without the assistance of a pump-maker or plumber, and which will be very effective for raising a great quantity of water to small heights, as in draining marshes, marl pits, quarries, &c., or even for the service of a house. It is exhibited in the subjoined diagram, where a b c d is a square trunk of carpenter's work, open at both ends, and having a little cistern and spout at top. Near the bottom there is a partition made of board, perforated with a hole e, and covered with a clack ; ffff repre sent a long cylindrical bag, made of leather or of double canvass, with a fold of thin leather, such as sheep-skin, between the canvass bags. This is firmly nailed to the board e, with soft leather between ; the upper end of this bag is fixed on a round board, having also a hole and valve. This board may be turned in the lathe with a groove round its edge, and the bag fastened to it by a cord bound tight round it. The fork of the piston rod is firmly fixed into, this board ; the bag is kept distended by a number of wooden hoops, or rings of strong wire ff, ff, ff, &c. put into it, at a few inches distance from each other. It will be proper to connect these hoops, before putting them in, by three or four cords, from top to bottom, which will keep them at their proper distances ; thus will the bag have the form of a barber's bellows or powder-puff. The distance between the hoops should be about twice the breadth of the rim of the wooden ring to which the upper valve and piston-rod are fixed. Now let this trunk be immersed in the water. It is evident, that if the bag be stretched from the compressed form which its own weight will give it by drawing up the piston-rod, its capacity will be enlarged ; the top valve will be shut by its own weight ; the air in the bag will be rarefied, and the atmosphere will press the water into the bags, When the rod is thrust down again, this water will come out by the top valve and fill part of the trunk. A repetition of the operation will have a similar effect; the trunk will be filled, and the water will be discharged by the spout.