418 TRANSACTIONS OF THE 



tain. Add to this the far greater cheapness, in most cases, of the 

 tile, and we see that there are but few soils requiring drainage 

 where it would ever be advisable to employ any other material. 



Assuming, then, that tiles are the cheapest and best aids to 

 under-draining, let us examine their action with a view of ascer- 

 taining the proper manner in which to construct the drain. 



Drains of the old fashion require of course to be made of con- 

 siderable size, that the dimensions of the passage for water may 

 be sufficiently large to compensate for its want of perfection. 

 Then, again, such drains — partly in consequence of the cost of 

 their constructiqn — are located chiefly in low parts of the land, 

 and only at long intervals, or Avhere they may tap springs or 

 deposits of water. Each drain is regarded as complete in itself, 

 not as a part of a system of drains aiding each other. It is, 

 therefore, made of a large size, and is filled with stone toward the 

 surface of the soil, that the water which runs over the surface to 

 this lower portion of the field may find easy access to the drain 

 by filtering down from the top. They are generally, if we may 

 use the expression, covered surface drains, and as^commonly con- 

 structed, they have little of the effect of thorough under-draining, 

 still, it is possible so to arrange them that they shall, for the time 

 of their duration, perform all of the work of tile-drains; as may 

 the tile replace the stone-drain for tlie purpose of surface-drainage. 



The object of under-draining is not simply to reliive the wetter 

 parts of the land of their surface water, but to remove from the 

 whole soil, to a depth of from thirty to thirty six inches, all 

 water which does not attach itself to the surface of its particles 

 by fn-ce of capillary attraction. This, and nothing less than 

 this, is thorough drainage, and this condition of the soil must be 

 attained before we can anticipate all of the good results which 

 are rightfully attributed to under-draining. Such a condition is 

 best etfected by the use of the tile, and it is w^ell always to bear 

 in mind these principles — that in thorough drainage the object is 

 to provide an outlet for water at the top of the water-level, and 

 that water which falls on the soil does not travel diagonally toward 

 the drain, but settles at once in a vertical direction, and thus 

 raises the level to such a height that the water enters tli« tile and 

 is carried away. It continues to flow until water from the upper 

 soil has ceased to descend to raise the position of that below. 



To illustrate this more fully, let us suppose a barrel, standing on 

 its end to be filled with soil, and that water be poured into it until 

 the soil is saturated — that is, until the space between the particles 

 are filled with water. If we now remove the bung of the barrel 



