HYDRAULICS AND HYDROSTATICS. 230 



Vessel for Spoutitiy Fluids. (Fig. 

 260.) This instrument consists of a 

 japanned tin vessel as represented in 

 the cut, usually from twenty-four to 

 thirty inches high, having five pipes or 

 jets, with exactly the same sized aper- 

 tures fixed on the side of the vessel at 

 equal distances apart ; the top of the 

 vessel is enlarged for a reservoir, and 

 the whole is mounted on a circular 

 base. 



In estimating the lateral pressure of 

 liquids, the vertical height must be 

 taken into the account ; since the ef- 

 fective force with which a liquid acts 

 against any given point in the side of 

 the containing vessel will depend on 

 the depth of that point beneath the 

 surface of the liquid. 



This will appear from the manner 

 in which water flows from apertures in the side of a cistern, 

 as the velocity of the stream will always be exactly pro- 

 portioned to the distance of the point of discharge from the 

 superior surface, and the consequent degree of pressure 

 which takes place. Suppose a vessel, A, to be filled with 

 water, and to have three or more tubes or pipes, B, c, D, of 

 equal lengths and diameter, fitted into lateral apertures at 

 different heights ; then if the liquid were suffered to flow 

 from the pipe D alone, the others being stopped, a greater 

 quantity of water would be discharged in a given time than 

 by the pipe c alone, and a greater quantity would issue 

 from the latter in the same time than by the pipe B only ; 

 the water being kept at the same level, so as to maintain an 

 equality of pressure during the whole time it was flowing. 

 And if all the pipes were opened together, the water would 

 spout to a greater distance from the pipe D than from either 

 of the others. 



The quantity of water spouting from any hole in a given 

 time, must necessarily be as the velocity with which it flows ; 

 and if, therefore, the hole D is supposed to be four times as 

 deep below the surface A, as the hole B is, it follows that D 

 will discharge twice the quantity of water, that can flow 

 from B in the same time, because 2 is the square root of 4. 



