482 TRANSACTIONS OF THE AMEHICAN INSTITUTE. 



book requires to be pvoteftcd from the weather; but if covered with a thin 

 coating- of litne phister, it will last for years. Hard stone i.s not much used 

 in consequence of th(j expense of working" it. The bricks used are badly 

 made, and require a covering' of plaster or coating of oil or coal-tar to pre- 

 vent them I'rom crumbling-. Iron also requires oil or tar to preserve it 

 from oxidation, but zinc will last many years with little or no decay. 



The items read by the Chairman elicited considerable discussion, after 

 which the regular subject, resumed from the last evening, was taken up. 



Pumps. 



Mr. E. P. Watson said, perhaps there is no machine for domestic use on 

 ■which there has been so much ingenuity displayed as the pump, the valves 

 of which, we are aware, have been the cause of much trouble, and pumps 

 with many valves are looked upon with disfavor. To overcome this objec- 

 tion pumps have been made without valves, and of different forms, but 

 only with partial success. The common form of valve in the old-fashioned 

 pump, is the ordinary box valve, or clapper, opening upward. This style 

 of valve is objectionable, as, when the water is low, the valve becomes dry 

 and will not work until water is thrown in. The ball valve, in rising and 

 falling so rapidly, batters the seat and leaks; it is also difficult to make 

 "water-tight all around. The spindle valve is now generally used in force 

 pumps. The flap valve, sometimes called the butterfly valve, is simply a 

 door with a hinge: they are generally made of brass. The difficulty with 

 this style of valve is that it is not always tight, as, if it is not hinged 

 evenly, the seats will not fit so as to be water-tight. There is a mode of 

 raising water by the admixture of atmospheric air. If a vertical tube be 

 placed in a reservoir of water, and if a quantity of air be injected into it 

 at the bottom of the tube by a bellows or force pump, the water in the tube 

 will immediately rise to a higher level, and remain until the air has es- 

 caped at the top; and if the tube be of proper height, the water will over- 

 flow. This mode, however, does not appear to be an economical way of 

 applying force. There is another style of machine called the bag pump, 

 made of a bag of leather connected with the piston of a pump and placed 

 in the cylinder. In this pump there is very little friction, but it is proba- 

 ble that the want of durability would be its greatest objection. This bag 

 is alternately extended and contracted, like a bellows, by every stroke of 

 the piston, and raises the water without much friction in the pump. We 

 have also the rope pump, which is made of a single rope or a bundle of 

 ropes passing over a wheel above and a pulley below, moving with great 

 velocit}', which draws a certain quantit}' of water by its friction. The 

 water probably ascends with about half the velocity of the rope, and the 

 cohesion of the water is sufficient to prevent its falling or being scattered 

 by any accidental inequality of the motion. A pump tlmt was very popu- 

 lar, and even now much used in the country, is the chain pump. It consists 

 of an endless chain, moving over two wheels, downward without, and up- 

 ward within, a barrel. This chain has a number of discs or circular 

 plates attached at certain lengths, which, on passing through the barrel, 

 carry the water in a constant stream betbre them. An objection to this 



