FARM DRAINAGE. 



67 



A GOOD OUTLET. 



top of the barrel but also making it certain that sediment would 

 be deposited. Our cut on page 66 shows a faulty outlet with the 

 line of saturation in the soil extending back up the line of drain. 

 The outlet of 

 every drain 

 should be pro- 

 tected from 

 stock and al- 

 so from ver- 

 m i n. The 

 best way is 

 to build a 

 good wall of 

 stone, which 

 should extend 



down so as to have a firm foundation, and an iron grate should 

 be built in so as to protect the mouth of the tile from the en- 

 trance of rabbits, muskrats, etc. 



Laying Out the Drains. Having selected the outlet, 

 which will usually be indicated by the natural course of the sur- 

 face water, you should lay out your drains before beginning the 

 work of digging. Each field will need a different arrangement 

 of drains, suited to the lay of the land. In one field a single 

 main will answer, with laterals extending on either side and the 

 size of the tile in the main may decrease as you approach the 

 head. In another field two or more mains may be necessary 

 which can all be brought to the same outlet, or such mains may 

 enter the principal main some distance above its mouth. The 

 straighter we can lay off our drains, the better, because there 

 will be less friction when the water flows straight, and a straight 

 line being the shortest distance between two points, it will take 

 less tile; and if in mapping the drain the points of angles are 

 established, by stretching a line the exact line of the drain 

 can at once be determined, if it is necessary to open it for 

 examination. 



Most works on drainage give elaborate directions for level- 

 ing, and cuts of various instruments to be used for the purpose. 



