Chap. 3.3 Engine. 459 



It is evident that thefe fire engines fhould be able 

 to furnifh a continued tlream, and this can .only be 

 effected by employing the elafticity of the air, while 

 the pifton is rifing ; but in order to effect this, a dou- 

 ble force is required to put the pump in motion ; in 

 other words, a force capable of expelling the column 

 of water, and an equal force to comprefs the air. But 

 this is not an inconvenience, for, in cafe of fire, it very, 

 feldom happens that hands are wanting to affiil ; on 

 the contrary, it frequently happens that the aflemblage 

 of people is rather too numerous. 



Such is the engine which M. Briflbn has defcribed, 

 and it is, I prefume, that which is in common ufe in 

 France. ' Its fimplicity is admirable j yet I apprehend 

 that our Englifli fire engines are more powerful, and 

 furnifh a more uninterrupted ftream or current of wa- 

 water through the leathern pipe. In Fig. 3. is a re- 

 prefentation of our improved fire engine. This, the 

 reader will fee, is wrought by two forcing pumps, 

 which act alternately ; and the ftream is made con- 

 tinual from the fpring of air confined in a ftrong metal 

 veflel C C, in the fire engine A B, fixed between the 

 two forcing pumps D and E, wrought with a com- 

 mon double lever F G moving on the center H. 

 The piftons in D and E both fuck and force alter- 

 nately, and are here reprefented in their different 

 actions, as are alfo the refpedtive valves at I K 

 and L M. 



The water to fupply this engine, if there is no 

 opportunity of putting the end of a fucking pipe, 

 occafionally to be fcrewed on, into a moat or canal 

 (which would fpare much hurry and labour in cafe of 

 fire) is poured into the vefiel A B ; and being flrained 

 through the wire grate N is, by the preffure of the 

 atmofphere, railed through the valves K and M into 



the 



