USES OF WATER 113 



pumped. The pressure may be obtained, however, 

 directly from the pumps. In either case it is often trans- 

 mitted through miles of underground pipes to thousands 



FIG. 102. High Pressure Fire Service Streams. 



The four pumps are discharging 12,000 gallons per minute. The streams 

 are 600 feet long. 



of faucets. The fire protection of a large number of our 

 cities is dependent upon the water pressure of such a 

 system (Figure 102). 



Pascal discovered that pressure applied anywhere to a 

 body of confined liquid is transmitted by the liquid so as 

 to act with undiminished force on every unit 

 of area of the containing vessel. 



Suppose a vessel such as shown in Figure 103 

 to be filled with water to the level ab. Suppose 

 the area of the upper part of the vessel is one 

 square inch. Now if an ounce of water be poured 

 into the tube, an extra ounce of pressure will FIG. 103. 



