RULE FOR DETERMINING THE CONTENTS. 211 



this water was collected, and kept for the dry season 

 only, twenty or thirty barrels daily might be used. 



In order to prevent a waste of water on the one hand, 

 and to avoid the unnecessary expense of too large cis- 

 terns, their contents should be determined beforehand 

 by calculation. 



RULE FOR DETERMINING THE CONTENTS. 



A simple rule to determine the contents of a cistern, 

 circular in form, and of equal size at top and bottom, 

 is the following : Find the depth and diameter in 

 inches ; square the diameter, and multiply the square 

 by the decimal .0034, which will find the quantity in 

 gallons* for one inch in depth. Multiply this by the 

 depth, and divide by 31^, and the result will be the 

 number of barrels the cistern will hold. 



For each foot in depth, the number of barrels an- 

 swering to the different diameters are. 



For 5 feet diameter 4.66 barrels. 



6.71 

 9.13 

 11.93 

 15.10 

 18.65 



10 



By the rule above given, the contents of barn-yard 

 cisterns and manure tanks may be easily calculated 

 for any size whatever. 



* This is the standard gallon of 231 cubic inches. The gallon of 

 the State of New York contains 221.184 cubic inches, or 6 pounds at 

 its maximum density. 



