68 THE SCIENTIFIC PAPERS OF 



In the discussion of the Paper 



"DESCRIPTION OF TWO PAIR OF HORIZONTAL 

 PUMPING ENGINES," by Mr. E. A. COWPER, 



ME. C. TV. SIEMENS * said he was acquainted with the 

 pumping-engines at the Berlin "Waterworks, where there were 

 twelve powerful beam-engines, coupled in pairs at right angles 

 with fly-wheels, and working vertical pumps under a pressure of 

 160 feet head of water. The present double ring valves allowed 

 an easy and unrestricted motion of the water, as the joint cir- 

 cumferences of the four openings gave a large area of passage with 

 a little lift of the valves. 



With regard to the employment of the crank and fly-wheel for 

 pumping-engines, in place of the Cornish system of lifting the 

 water by the weight of the plungers, it was true that a large 

 fly-wheel with a great weight in the rim, running at a considerably 

 higher speed than the weight in the Cornish engine, had the 

 advantage of more vis inertice ; but only a limited fluctua- 

 tion in its speed was available, and the weight was never stopped 

 as in the Cornish engine, where the whole weight of the pump- 

 rods was stopped and started again at each stroke. It was there- 

 fore to be expected that a greater economy could be obtained by 

 the latter plan, in case of very great lifts, a larger proportion of 

 moving power being absorbed at the commencement of the stroke, 

 allowing the expansion to be carried to a higher degree by ad- 

 mitting of greater extremes of pressure in the stroke. He 

 accordingly thought there were cases, such as pumping from deep 

 pits, where the Cornish plan would prove the most economical, 

 the pump rods falling gradually by their own weight, and being 

 then lifted by the free action of the steam in the cylinder ; but in 

 many cases, such as low lift pumps, the horizontal direct con- 

 struction was preferable. He observed that the engines described 

 had not been designed for such a high degree of economy as was 

 attained in the Cornish engines, since the steam was cut off only 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineers, 

 1858, p. 57. 



