1()£ KEW ttYDRAULIC KNGINE. 



New engine for I n this new fituation the column A B no longer commifm- 

 che'ddcen^or I catcs with G > bllt a # s through F upon the upper part of the 

 column inclofed pifton H, and deprelfes it ; while the contents of the great 

 P ; pe- cylinder beneath that pifton are driven out through GGG, 



and pais through the opening at E into R. It may be ob- 

 ferved, that the column which acls againft the pifton is aflifted 

 by the prellure of the atmofphere, rendered active by the co- 

 lumn of water hanging in R, to which that aflifting preifure is 

 equivalent, as has already been noticed. 



When the pifton has defcended through a certain length, 

 the Hide or block, at T, upon the pit-rod, applies againft the 

 tail K of the tumbler, which it depreffes, and again overfets ; 

 producing once more the pofttion of the plugs D E, here- de- 

 lineated, and the confequent afcent of the great pifton H as 

 before defcribed. The afcent produces its former effect, on the 

 tumbler and plugs; and in this manner it is evident that the 

 alternations will go on without limit : or until the manager 

 fliall think fit to place the tumbler and plugs D E in the pofi- 

 tions of reft; ; namely fo as to flop the palfages F and G. 



The length of the ftroke may be varied by altering the po- 

 rtions of the pieces T and I, which will (horten the ftroke 

 the nearer they are together ; as in that cafe they will fooner 

 alternate upon the tail K. 



As the fudden ftoppage of the defcent of the column A B, 

 at the inftant when the two plugs wer^ both in the water way, 

 might jar and ihake the apparatus, thofe plugs are made half 

 an inch fhorter than the depth of the fide holes ; fo that in that 

 cafe the water can efcape direclly through both the fmall cy- 

 linders to R. This gives a momentary time for the generation 

 of the contrary motion in the pifton, and the water in G G G, 

 and greatly deadens the concuflion which might elfe be pro- 

 duced. 



Former attempts to make preflure engines, upon the prin- 

 ciple of the fteam engine, have failed, becaufe water not be- 

 ing elaitic could not be made to carry the pifton onwards a 

 little, fo as completely to ftiut one fet of valves and open an- 

 other. In the prefent judicious conftruction the tumbler per- 

 forms die office of the expanfive force of fteam at the end of 

 the ftroke. 

 Rate of work There are feveral other engines of this conftru&ion at work, 

 by thefe engine* The general rate of working of all thefe engines is, that four 



feet 



