432 Di/charge of Fluids, &c. [Book VII. 



of the aperture as ten to fixteen. It is nearly the fame 

 when water ftows through lateral apertures. The 

 contraction of the ftream is a proof of what has been 

 before ftated, viz. that withinfide a veffel, the lateral 

 particles direct themfelves towards the orifice with a 

 motion more or lefs oblique ; and this oblique motion 

 may be decompofed into two forces, the one parallel 

 to the plane of the orifice, and which contracts the 

 ftream j the other perpendicular to the fame plane, 

 and the only one which produces the efflux. 



This contraction occurs alfo when water is made to 

 flow through pipes, and that at the entrance of the wa- 

 ter into the pipe, and not at its exit, where the ftream 

 preferves a cylindrical form. I (hall prove that this 

 contraction dimmifhes, in a fenfible manner, the quan- 

 tity of water which would naturally flow. 



In order to aicertain thefe facts by experiments, 

 many have been made. In all the following infiances 

 the orifices, through which the v/ater flowed, were 

 pierced perpendicularly through plates of copper of 

 about one-twenty-fourth of an inch thick, and the rime 

 of each experiment is reduced to one minuet. 



