216 FIELD, FOREST AND FARM 



cordingly we proceed to dig a number of small 

 ditches, of a depth somewhat greater than that at- 

 tained by plant-roots, and we fill the bottom of these 

 ditches with small stones, on which we finally throw 

 back the earth we have removed. These under- 

 ground ditches are suitably inclined, and all empty 

 at the lower end into a main canal. The water sat- 

 urating the soil collects in these ditches, filters 

 through the layer of pebbles, and empties into the 

 main canal, which carries it off to some river or 

 other stream. Our marshy soil is now like the pot- 

 ful of earth with a hole at the bottom, the bit of 

 broken tile, and layer of little pebbles : the air has 

 free access and brings fertility with it. This opera- 

 tion of ours is called drainage, a word formed from 

 'drain,' which is both a verb and a noun. In the 

 latter sense we apply it to the narrow ditch dug for 

 carrying off superfluous water. 



"A drainage system like that just described is 

 the simplest possible, but there is one serious objec- 

 tion to it: the layer of small stones soon becomes 

 clogged with soil washed down by the water, and 

 the latter can no longer run off. Hence it is cus- 

 tomary to use fagots instead of stones, since they 

 offer less obstruction. But still better results are 

 obtained with earthenware conduits laid in the 

 ditches. Sometimes these conduits take the form 

 of drain-tiles such as are used on roofs, and they 

 rest on sills or ground-pieces of the same material; 

 or, again, they may be tubular in form, the succes- 

 sive sections loosely fitted together so that the water 



