4 IMPROVEMENTS IN HYDRAULKENGINES. 



8. The Schemnitz engine will always raife water to a. 

 height nearly equal to that of the original all, from one refer- 

 voir to another, fuppofing th^original fallof any height what- 

 foever, as 100 feet. 



Mr. Goodwyn's engine will not raife w;ter from one refer- 

 voir to another fo high as thirty feet in aiy cafe whatfoever, 

 as there cannot be a complete vacuum ibrned by it in the air 

 chamber, but only an approximation to one 

 Mr. Go(vJwyn*s From this companion it will follow, tha wherever the on- 

 preferable 1 , and 8 ma * ^11 °^ water * s tefil than thirty-two fee, Mr. Goodwyn's 

 leaft coftly in engine will be much preferable to the Scheimitz ; as, from the 

 (mail elevations. ?th artic . e f the compar ;fon, ft mav be mide of the cheapeji 

 materials, of ftrong iionden cajks and ivooien pipes ; whereas 

 the Schemnitz engine, from the 6th article, mull be made of 

 the ftrongeft, and of courfe molt coftly materials, of caft iron 

 at leaft, and that of confiderable thicknefs. 

 The Schemnitz But wherever the original fall exceeds tin height of thirty 

 greater depths. ^ eefc much, and it is required to raife the waer to nearly the 

 fame height, then the Schemnitz engine appears to be pre- 

 ferable ; as, in all probability, the fewer lumber of parts 

 which it will, in this cafe, require in its conftri6tion, will more 

 than compenfate for its coftly materials. 

 Pifton engine When it is required to raife water to a heiglt, much greater 



g!fat°dep e ths. than that of the original fall, above the firft evel, or from a 

 greater depth ; either from the original fall beng ftiort, or the 

 required height being great, an engine in which the preffure 

 of the water is made to act by a pifton in an apparatus limilar 

 to that of the fteam engine, (one of which is defcribed in your 

 • Journal for March) will be preferable to either of the above. 

 Comparifon of The comparison of thofe engines may be brought to this one 

 eines. reeen " point: wherever Mr. Goodwyn's engine can be ufed, with a 

 fingle continued pipe for elevating the water, and without a 

 fucceflion of refervoirs, it feems to be the cheapeft. 



Where Mr. Goodwyn's engine cannot be ufed without viola- 

 ting this condition, but the Schemnitz can, it promifes to be 

 the next in point of cheapnefs, from its fimplicity, abfence of 

 friftion, and fmall number of working parts. 



But when neither Mr. Goodwyn's engine nor the Schemnitz 

 can be ufed without a number of refervoirs, then the pifton 

 preffure engine probably ought to be preferred ; but this will 

 much depend on the number of refervoirs, for perhaps one or 



two 



