CISTERNS. 



the quotient will be the number of gallons. Divide the 

 number of gallons by 31, and it will give the number of 

 barrels. 



EXAMPLE. What must be the capacity of a cistern to 

 contain the water running from a roof 40 feet long by 30 

 wide, for 2 months : estimated fall of rain 7 inches ? 



SOLUTION. 480 inches, length, x 360 inches, width, x 7 

 inches, depth of rain, = 1909600-^- 231 = 8266f galls. Ana. 



NOTE. To ascertain the necessary dimensions of a cis- 

 tern large enough to contain 8266f gallons, consult the 

 foregoing table. It will there be found that a cistern 13 

 feet in diameter contains 827 gallons for each 10 inches in 

 depth. To give the cistern 10 times that depth, or 100 

 inches (8-J- feet) will make it contain 8270 gallons. Hence 

 a cistern 13 feet in diameter, and 8-J- feet deep, will be large 

 enough. 



To further aid the inquirer in ascertaining the requisite 

 diameters of cisterns for the above purposes, we subjoin 

 an additional 



TABLE, showing the contents of circular cisterns in barrels 

 for each foot in depth. 



5 feet 4.66 



6 " 6.74 



7 " 9.13 



8 " 11.93 



9 " 15.10 



10 " 18.65 



