MISCELLANEOUS FARM CONVENIENCES 



237 



three hundred gallons in each compartment, which 

 would require a tank about four feet in width and six 

 feet in length and four feet in depth. These figures 

 embrace more cubic feet of tank than necessary to meet 

 the foregoing requirements. It is a good plan to leave 

 a margin of safety. 



It is usual to lay a vitrified sewer, four inches in 

 diameter, from below the bottom of the cellar to the 



Figure 239. Septic Tank, a double antiseptic process for purifying 

 sewerage. 



septic tank, giving it a fall of one-eighth inch in ten 

 feet. The sewer enters the tank at the top of the stand- 

 ing liquid and delivers the fresh sewerage from the 

 house through an elbow and a leg of pipe that reaches 

 to within about six inches of the bottom of the tank. 

 The reason for this is to admit fresh sewerage without 

 disturbing the scum on the surface of the liquid in the 

 tank. The scum is a protection for the bacteria. It 

 helps them to carry on their work of destruction. The 

 same principle applies to the second compartment. 

 The liquid from the first compartment is carried over 

 into the second compartment by means of a bent pipe 



