DISEASES OF CATTLE 49 



and may connect with the same tile as that coming from the dairy 

 barn. 



The Size of Septic Tank and Irrigating System. The size of 

 the septic tank depends somewhat upon the amount of sewage run 

 through the tank and the consistency of the sewage. For average 

 conditions the last two compartments should hold the average dis- 

 charge in twenty-four hours, and the irrigating system should be of 

 equal capacity to hold the sewage from this compartment. How- 

 ever, the larger the tank the greater will be the chance for the or- 

 ganic matter to thoroughly decompose, and at the same time the ir- 

 rigating system can be of greater capacity, irrigating a larger tract 

 of land. 



Necessity of Compartments. Since the decomposition of the 

 sewage depends upon the action of bacteria, it is essential in order to 

 have the process go on effectively that the germs should not be dis- 

 turbed to any great extent. Sewage, as a rule, when it comes from 

 the house or dairy barn, runs into the tank with a rush, which has 

 a tendency to roil the sewage in the tank. To overcome this sudden 

 rush a partition should be put across the septic tank close to the inlet 

 of the tank, which is supposed to prevent the disturbance in the 

 second, third and fourth compartments. However, it is quite im- 

 possible to regulate the force of sewage in such a manner as to pre- 

 vent any disturbance in the second tank. For this reason it is advis- 

 able to put a third partition in the tank, which will give the germs a 

 chance to act thoroughly upon the sewage before it enters the dis- 

 charge tank, or last compartment. 



As the sewage travels from one tank to another it is gradually 

 purified, and as it flows into the discharge tank all organic matter 

 is in a liquid or semi-liquid state. At this point the sewage is prac- 

 tically deprived of any disagreeable odor, and that which is still re- 

 tained is not objectionable. To prove the efficiency of this method 

 of purification, sewage after passing through the tank, being thor- 

 oughly decomposed, can be kept for weeks at a very favorable tem- 

 perature, showing no signs of the development of putrefactive odors. 

 It should require from three to four days, however, for sewage to 

 pass through this tank to thoroughly deodorize it. Three partitions 

 in a tank, as described above, have proven very efficient. However, 

 a tank with two compartments is very satisfactory, but in no case 

 can a tank without compartments be recommended. 



Location of Septic Tank. There should be a slight fall from 

 the stable to the septic tank, and from this tank to the irrigating 

 system. A septic tank can be located as far as convenient, or as near 

 as desirable, to the traps. This is a matter that depends upon con- 

 ditions entirely. However, in all cases the inlet and outlet drains 

 of the system, as far as the point of irrigation, should consist of 

 sewer pipe with joints cemented. A preferable location for the tank 

 is about a foot to eighteen inches in the ground. This prevents 

 freezing, which checks decomposition. However, there are in- 

 stances in which the slope of the ground from the stable to the ir- 

 rigated field is so slight that the septic tank needs to be put above 



