Polytechnic Association Proceedings. 785 



between the two levels. The concussion or thumping of the piston 

 pump is very great. In the engines used in Holland, one is worked 

 by high pressure, and the other by low pressure. Eleven columns 

 of water are sent up Tvith one stroke of the piston to a height of 

 eleven to fourteen feet, and many tons of water are thrown up at 

 every revolution of the engine. This style of pumpiug has many 

 objections, and the American centrifugal pump would do the same 

 amount of work with much less loss of power, and less liable to 

 get out of order. 



Mr, Charles E. Emory stated that at the Brooklyn Water Works 

 they use two pumps, working alternately. There is not so great 

 a loss as would at first be supposed, as in the first part of the 

 stroke the force is great, but when the water is once in motion, so 

 much power is not required. The centrifugal pump does best with 

 a low head of water, and it will hardly work at all with a high 

 head. The mere act of putting a mass of matter in motion is not 

 difiicult. The waste is only when the force is used to move what 

 is not required. In the Brooklyn engines the air pump is used as 

 a spring to compress the air, and give back force to the water. 

 In a well constructed pump the air barrel is very necessary. A 

 reciprocating pump with an air chamber does not waste power. 

 Any unevenness of motion can be overcome by counter-weights. 

 Counter-weights when first used on locomotives increased the speed 

 very much; fourteen miles an hour was the ordinary speed without 

 them, but the use of counter-Aveights doubled the speed to twenty^ 

 eight miles. If the pump is placed below the water level, so that 

 there is no vacuum formed, the water will flow quite readily into 

 the pump, and a gain is thus attained. Much has been said about 

 pumpiug hot water, and the difficulty of forming a vacuum on 

 account of the vapor from the hot water, but he had seen water at 

 212 degrees pumped without any trouble whatever. 



Mr. S. Mcllroy stated that he pumped hot lye at a temperature 

 of 180 to 212 degrees, but the only pump that he could find to 

 do this was the Springfield pump. 



Dr. Vanderweyde added that there was a device patented for 

 the use of an India rubber diaphragm in the chamber of the air 

 pump, but this is very often broken. He had contrived an air 

 chamber for the exhaust, and another for the force pump side. 

 After some further discussion, the Association adjourned. 



[Inst.] 50 



