110 VARYING INCLINATION. 



and cheaply removed only by drains devised for 

 and devoted to that object. Appropriate drains at 

 (bhh), for instance, as indicated in the dark vertical 

 lines above, are found to do the service of many 

 parallel drains, which as frequently miss as they 

 hit those furrows or lips in the horizontal outcrop 

 of water-bearing strata, which continue to exude 

 wetness after the higher portions are dry. 



" A consideration, too, of the varying inclination 

 of surface, of which instances will frequently occur 

 in the same field, necessitates a departure from 

 uniformity, not only in direction, but in the inter- 

 vals between the drains. Take, for instance, the 

 ordinary case of a field in which a comparatively 

 flat space intervenes between quickly rising ground 

 and the outfall ditch. It is clear that the soak of 

 the hill will pervade the soil of the lower ground, 

 let the system of drainage adopted be Avhat it may ; 

 and therefore, supposing the soil of the hill and fiat 

 to be precisely alike, the existence of bottom water 

 in a greater quantity in the lower lands than in the 

 higher, will call for a greater number of drains. It 

 is found, too, that an independent discharge, or 

 relief of the water coming from the hill at (h) 

 should always be provided, in order to avoid any 

 impediment by the slower flow of the flatter drains. 



" Experience shows that, with few exceptions, 

 hollows or slacks observable on the surface, as at 

 (6&), have a corresponding undulation of subsoil; 



