Chap. 3.] or Jets d'Eau. 443 



two jets d'eaux proceeding from the fame refervoir, 

 and flowing from their ajutages with an equal degree 

 of velocity, the greater will, in the firft place, expe- 

 rience lefs friction ; and fecondly, it has a greater 

 mafs, and confequently more power to overcome the 

 obftacles which may oppofe it. 



But, though large jets d'eau elevate water higher 

 than fmall ones, they do not expend a greater quantity 

 in proportion ; for the quantity of water difcharged is 

 as the product of the aperture of the ajutage by the 

 degree of velocity at the time of the difcharge ; and 

 this velocity is the fame in both, no allowance being 

 made for the friclion. 



In order to make large fountains elevate water 

 higher than fmall ones, it is evidently neceflary that 

 the conducting pipes fliould be fufficiently large to 

 furnifh water in abundance; for if they are fmall, ex- 

 perience proves that the fmall fountains in that cafe 

 will elevate water higher than larger ones j it follows, 

 then, that the diameter of the pipe, which conveys the 

 water, fhould be in proportion to that of the ajutage, 

 in order to elevate the water to the greatefl poffible 

 height. 



If we compare two different jets d'eau, and are de- 

 firous that each mould elevate water to the greateft 

 poffible height, it is neceflary that the fquare of the 

 diameters of the conduit pipes fhould be in proportion 

 to each other in the compound ratio of the diameters 

 of the ajutages and the fquare root of the altitudes of 

 the refervoirs. Thus, if it is known by experiment 

 what the diameter of a conduit pipe fliould be, to 

 fupply an ajutage 5f given dimenfions, it may be eafily 

 determined what the diameter of another pipe fliould 

 be to furnifh another ajutage of a determinate fize, the 

 height of the refervoir being alfo given. 



It 



