868 BEPORT— 1892. 



The actual causes of tbe violence which is admitted to occur are then shown 

 to be partly internal, due to avoidable errors in construction, and partly and 

 principally to the concussion of the waste valve in closing at a high speed. 



The author then mentions the attempts made by various inventors to diminish 

 this violence by cushioning the blow of the valve, which, while partially success- 

 ful in their immediate object, result at the same time in impairing the efficiency 

 of the machine, and shows that the explanation sometimes given of this result — 

 viz., that it prevents the instantaneous action imagined to be necessary — i» 

 untenable. The true reason of the observed effect is shown to he merely that the 

 slowness of shutting produced by cushioning chokes the flow, and, this being so^ 

 a method is at once suggested of shutting slowly without choking the flow, and 

 consequently without impairing the efficiency of the machine. 



It having been thus shown that all existing causes of violence are removable, 

 it does not appear that there is any other reason to prevent the extended use of 

 this principle, and in some respects it is much more suitable for use on a large 

 scale than on a small, notably on account of the smaller coefficient of friction in 

 large pipes. 



A large engine was constructed to prove the above ideas in practice and dis- 

 cover any unforeseen practical difficulties. The proportions of this engine were 

 deduced from theoretical considerations, discarding the empirical rules formerly in 

 use, as it was found that the theory of the machine indicated the advantage of 

 proportions differing from these. It was also evident that the periods of time 

 during which the main valve was open and shut would be of great importance, 

 and the most suitable times were therefore determined and machinery designed 

 to give the valve exactly this motion. Very much higher velocities were also used 

 in the flow-pipe than had hitherto been used, with the effect of greatly increasing- 

 the power of a machine of given size. 



The flrst engine made on this basis was successful, and three others have since 

 been made differing in some practical details. The principal features of these 

 engines are the use of an annular slide valve for the waste valve, moved by a cam 

 in order to obtain exactly the motion required and bring the valve to its seat 

 without any impact, the gradual shutting of this valve being prevented from 

 checking the momentum of the water by the provision of a space into which some 

 of the water flows during the shutting of the valve. This space or antechamber 

 is emptied of water during the opening of the main valve, being provided with an 

 air-valve which admits air at that time, and allows the air to escape as the 

 chamber fills with water. 



Precisely similar engines have been also used to compress air, the air being 

 compressed in a chamber similar to the antechamber spoken of above, and its 

 quantity being capable of exact regulation by placing the air-valve in a tube, the 

 depth of which below the roof of the chauiber is regulated by a screw. 



The general results obtained from these engines are — 



1. Entire absence of violence as predicted. An indicator diagram of the in- 

 ternal pressLire exhibited further shows this. 



2. Very high efficiency, amounting to over 70 per cent, when pumping water^ 

 and over 80 when compressing air. 



3. That the construction is simple and much less costly than the ancient 

 method, and the management of the engines is easy and the wear slight. 



4. Evidence that a similar construction is equally feasible for engines having 

 flow-pipes 3 feet or 4 feet diameter. 



In short, it has been established as a fact of actual experience that the simple 

 and useful principle of the hydraulic ram may safely and very advantageously be 

 extended to nearly all cases where water-power is used for pumping or for 

 compressing air, and that there is no need at all to continue in future the use of 

 the antiquated indirect methods, but there are very strong reasons for not doing so. 



The author farther mentions the result of recent experience in using still 

 higher velocities in the flow-pipe with a view to still further increasing the power 

 of engines of a given size. A'elocities eight times as great as used in ordinary 



