296 THE YOUNG FAKMER'S MANUAL. 



drain with a large throat should never be less than three feet 

 deep. The larger the throat is, the deeper a drain ought always 

 to be made ; because the wider the space of the throat the more 

 liable a drain is to become obstructed by the dirt caving in. 

 Throats that are much deeper than their width are less liable to 

 become obstructed than those are which are wider than their depth. 

 Tile, the calibre of which is twice as deep as it is wide, will dis 

 charge water with greater rapidity than those will having round, 

 or half round calibre. (See MANUFACTURING TILE, 436.) 



HOW TO DETERMINE THE PROPER DEPTH FOR DRAINS. 



408. A man who has had a good share of experience in under- 

 draining will be able to conjecture, in most instances, about how 

 deep ditches should be cut in order to operate most effectually. 

 But the correct and sure way is, to " cut and try." Let the 

 ditches be cut about thirty or thirty-six inches in depth, not in a 

 very wet time, nor in a very dry time. Now, if by digging 

 thirty inches deep most of the veins of water seem to be cut off, 

 and but little bubbles up from the bottom of the ditch, it is use 

 less to dig deeper. "When it is very evident that a field needs 

 draining, and ditches have been cut thirty inches deep, and no 

 veins of water are reached, it is very conclusive evidence that the 

 ditches should be sunk deeper. Again : when ditches have been 

 cut thirty inches deep, and most of the water issues from the sides, 

 and but little or none bubbles up in the bottom, there will -be no 

 necessity of sinking them deeper for the sole purpose of cutt'ig 

 off the veins of water. It is no uncommon occurrence to see 

 about all the water that has been the cause of rendering the soil 

 wet, flow into a ditch at twenty or twenty -five inches from the 

 surface of the ground, at the sides of the ditch. When such is 

 the case, the expense of sinking a ditch more than thirty inches 

 deep except for the purpose of securing a bottom with a true 

 grade, or for large tile (see Fig. 132) would be entirely useless. 

 When a ditch has been sunk thirty inches deep, and the subsoil 

 appears to be full of water, and but little water flows into the 



