53 



creased. Where it is found that the water accumula- 

 ting, or to accumulate from the different branches, would 

 be greater than could be discharged through the largest 

 sized tiles, a double or even triple row may be laid 

 together in the same trench. 



1^11] 0f grains. 



The depth of the drains is the most important point 

 connected with the subject, and one which will require 

 the exercise of the most careful judgment. The first 

 care should be to secure a proper outlet, at whatever 

 depth it may be necessary to go to obtain it. To this 

 point there must be a continuous descent of at least one 

 foot in eight hundred, uninterrupted by any depressions, 

 since these would cause an accumulation of deposits, 

 which would in time choke the drains. The earth in 

 the Prospect Park consists, first, of a few inches of soil, 

 then a layer of clay, varying in thickness, sometimes 

 alternate layers of clay and sand, beneath which is hard- 

 pan or drift. In the larger depressions, there is some- 

 times quick-sand beneath this, and scattered through the 

 drift an innumerable quantity of boulders, which defy 

 the precise location of drains, except on the ground 

 itself. As a general rule, the main drains should be from 

 three to four feet below the surface, and the lateral 

 drains from two feet six inches to three feet. An increase 

 of depth adds largely to the expense, especially in the 

 hard-pan, where it will cost almost as much to keep the 

 picks sharp as the labor is worth, and in the end adding, 

 perhaps, no benefit to the ground. Still, no question of 

 economy should prevent the drainage being thoroughly 

 accomplished. 



