372 



STATE BOARD OP AGRICULTURE. 



of the strata can be tested by pouring water down the pipe. Tlio size of the 

 well will depend on the area to be drained. It will probably be better to con- 

 struct as many Avells as may be needed, each with an internal diameter of six 

 or eight feet, rather than try lo make fewer wells of larger size. If the strata 

 take water with great avidity, a two-inch drive-well might answer; but from 

 considerations to be mentioned further on, such wells are not likely to be per- 

 manent. 



How Constructed. 



In the construction of these wells, certain important considerations are to be 

 taken into account : First the well must have as large an area as possible in 

 contact with the water-taking strata; second the water that enters the well 

 must be as pure as possible. The first condition is secured by sinking a large 

 well so deep into the strata that water will escape from the sides as well as 

 from the bottom. The second condition is important, because the drainage 

 water from all land, and especially from marshes, holds in suspension a fine 

 dirt, termed silt, which is deposited when the water comes to a rest, covering 

 everything with a crust which would, in time, choke up the 

 best drainage well ever made. AV"e can prevent this dirt 

 from getting into the well by the construction of settling 

 or silt basins, whicli first receive the Avater and discharge 

 it into the main well. The important thing in the construc- 

 tion of these silt basins is to make them large enough to 

 hold considerable water, and to have the outlet of the out- 

 going pipe its diameter below that of the outlet of the 

 incoming pipe. These settling basins may also receive 

 the surface water. The construction is shown in Fig. 170, 

 in which A is the settling basin and B the main drainage 

 well. 



More than one settling basin might be constructed on 

 different sides of the well, if necessary. I would make the 

 settling basin four feet in diameter, with a depth of three 

 Outlet of drain. rig;"4. feet below the tile coming in. 



The main drainage well should probably be filled with large, loose stones at 

 least to the bight of the drain. However well drainage wells might answer, 

 they can never be superior to a free outlet. 



Protection to ouiletn. 



The outlet to under-drains should be protected by some construction, as 

 shown in Fig. 4, that will prevent the earth from falling in front of the drain. 

 The best construction is a retaining wall of masonry laid in hydraulic cement. 

 There should also be a coarse grating in front of a tile drain to prevent vermin 

 from getting in. Coons, muskrats, and rats have been known to run up tile 

 drains as far as they could go, and finally get lodged, and form an obstruction 

 to the flow of water. The outlets should be free; that is, above the surface 

 of still water, as standing water in a drain is liable to cause a deposit of silt. 

 Common porous tiles should never be used for an outlet, as they are destroyed 

 by freezing when wet. For the IG feet nearest the outlet, either glazed tile 

 or a triangular or diamond-shaped box of wood should be used. In nearly 

 every kiln there are a few tiles burned so badly as to be in part vitrified. Such 

 tiles, if of good shape and full size, would answer for outlet tiles. 



