444 Artificial [Book VIL 



It has been proved by experiments, that when the 

 diameter of the ajutage h half an inch, and the height 

 of the refervoir fifty-two feet, the diameter of the pipe 

 which conducts the water ought to be three inches and 

 a quarter; and that for an ajutage of half an inch dia- 

 meter, the height of the refervoir being fixteen feet, 

 the diameter of the pipe ought to be about two inches 

 and one-third. There is no inconvenience in making 

 the conduit pipe of a greater diameter than is required 

 by this rule ; but on the contrary, there would be an 

 inconvenience in making it of a fmaller diameter. 



Sometimes the ajutage is made in the form of a 

 cone, and fometimes in that of a cylinder ; but thofe 

 who conceive that it is indifferent in which of thofe 

 forms it is made are miftaken, for the cylindrical form 

 is by far the moft difadvantageous. 



By comparing many experiments made upon artifi- 

 cial fountains, it has been determined, that the differ- 

 ences between the altitudes of vertical jets and the 

 height of their refervoirs, are to each other as the 

 fquare of the altitudes of the former. If then it is 

 known what quantity of water a jet elevates at a cer- 

 tain height of the refervoir, the quantity which any 

 other jet of a given height will elevate, compared 

 with the height of its refervoir, may be eafily found 

 by the rule of fingle proportion. 



When it is neceffary to bend the conducting pipes, 

 the utmoft care mould be taken to avoid bending 

 them at right angles, for the ftriking of the current 

 againft thefe angles very confiderably diminifhes the 

 velocity. 



The following table will greatly facilitate the appli- 

 cation of thefe principles. 



The heights of jets, and the correfpondent heights 

 of refervoirs, are found in the two firft columns. The 



third 



