EQUILIBRIUM. 



its surface are in the same horizontal plane, 

 idea is expressed in the 

 familiar saying, water 

 seeks its level. This 

 is true whether the 

 liquid be placed in a 

 single vessel or in sev- 

 eral vessels that com- 

 municate with each 

 other. 



234. Communi- 

 cating Vessels. 



When any liquid is 

 placed in one or more 



EBSITY 



The central 



FIG. 77. 



of several vessels communicating with each other, it will 

 not come to rest until it stands at the same height 

 in all of the vessels, so that all of the free surfaces lie 

 in the same horizontal plane. This principle is prettily 

 illustrated by the apparatus represented in Fig. 77. It 

 consists of such communicating vessels containing a liquid. 



(a.) This important principle that " water seeks its level" finds a 

 gigantic illustration in the system of water-pipes by which water is 

 distributed in cities and large towns. Brought or pumped into an 

 elevated reservoir near the city, the water flows, in obedience to the 

 force of gravity, through all the turns and windings of all the pipes 

 connected with the reservoir, and is thus brought into thousands of 

 buildings. Into any of the rooms of any of these houses the water 

 may thus be led, provided only that the ends of the pipes be below 

 the level of the water in the reservoir. 



(&.) Among the many other results of this tendency of water to 

 seek its level may be mentioned the action of springs and Artesian 

 wells, the use of locks on canals, the spirit-level, the flow of 

 streams, etc. 



