460 fbs Fire Engine. [ B ook VI I . 



the barrels of D or E, when -either of their forcers 

 afcend; whence again, upon their defcent, ic will be 

 powerfully propelled into the air-veflel C C, through 

 the valves I and L by turns: the common air then 

 between the water and the top of the air-vefTcl C C 

 will from time to time be forcibly crowded into lefs 

 room, and much comprefTed ; and the air being in that 

 condenfed ftate pofTeflTed of a flrong and lively fpring, 

 and always endeavouring to dilate itfelf every way 

 equally in kich a circumftance, bears ftrongly both 

 againft the fides of the veffel wherein it is confined, and 

 the furface of the .water thus injected ; and thus pro- 

 duces a conftant regular (bream, wlych rifes through 

 the metal pipe P into the leather one Qj and this lat- 

 ter being perfectly flexible, may be led about into 

 rooms and entries, as the cafe may require. 



Should the air contained in this vefiel be compreffed 

 into half the fpace it took up in its natural (late, the 

 fpring of it will be nearly doubled 5 and as before it 

 equalled and was able to fuftain the preffure of the at- 

 mofphere, fmce it has now a double force, by the 

 power of that fpring alone it will throw water into air 

 o-f the common degree of denfity about thirty feet 

 high. And fhould this compreffure be (till aug- 

 mented, and the quantity of air, which at firft filled the 

 whole veffel, be reduced into one-third of that fpace, 

 its fpring will be then able to refifr, and confequently 

 to raife the weight of a treble atmofphere ; in which 

 cafe it will throw up a jet of water fixty feet high. 

 And fhould fo much water again be forced into the 

 vcffel as to fill three parts of the capacity, it will be 

 able to throw it up about ninety feet high : and where- 

 ever the fervice (hall require a ftill greater rife of wa- 

 ter, more water muft be forced into this vefiel; the 

 air therein being thus driven by force into a ftill nar- 

 rower 



