HYDRAULIC ENGINE. 37 



When the two pinions turn (fo that their upper teeth may Its aaion. 

 conftanlly approach each other, while the lower recede,) 

 the water which lies between their teeth in the lower part D 

 of the chamber, will be carried round till it arrives at the 

 part C, where it will be comprefled by the continual augmen- 

 tation of water, which is brought thither between the teeth, 

 (or rather by the perpetual diminution of the fpace between 

 the two uppermoft teeth that touch ihe chamber). So that the 

 fluid will enter the pipe F, and be forced to the intended 

 place. 



Thus far I have tranflated from Monf. de Serviere. Tlie Remarks an the 

 machine appears to be ingenious, and though liable to the '^"S'"^' 

 objedions of wear which you very properly urged againft the 

 fchemesofO. B. and others*, feems preferable to them in feveral 

 refpeds. I think it would bean improvement, to caufe the axis A 

 and B to drive by a connexion of external wheel-work, inflead 

 of depending upon their interior teeth, which require to be well 

 figured and fitted, and kept fo, by not loading them with 

 prefTure of one furface againft the other. It feems fcarcely 

 necetTary to remark, that we have better methods of connec- 

 tion for work at a diftance in our cotton gear and elfewhere, 

 than the Aiding piece I ; and laftly, I would propofe it as a 

 mathematical exercife to determine the law of the velocity of 

 the fluid through F, when the rotation of the machinery is 

 uniform. 



Among the machines which I believe have been confidered p'^ engines re- 

 as of later date, but are found in this work, are the engine 

 mentioned in Defaguliers, for railing water by a lofing and Lofing and gain- 

 gaining bucket, and regulated by a fly ; the chain pump, for p? f"cket. 

 which Cole had a patent, but which is4nown to have been 

 of very ancient ufe in the Chinefe Empire; the horfe mill Adam Walker's 

 worked by the wheels of a carriage, as lately propofed by the "'' ^ ""' • 

 ingenious Adam Walker j and the gouty chair of Merlin, 

 worked by two fmall handles conneded with a pair of fmall 

 wheels attached to the fore feet. 



I am. Sir.;, with efteem. 



Your obliged Reader, 



R. B. 



* Phllof. Journal. Quarto feries, IV. 468., 



