26 



earth made up of fine particles it is liable to become clogged by 

 the infiltration of silt. 



Such drains can be made silt-proof, and consequently perma- 

 nent, by enclosing or surrounding them with silt-excluding mate- 

 rials, such as boards (for a foundation), green brush, turf, old 

 hay or straw, coarse gravel, etc., according to availability and 

 other circumstances, which will readily suggest to the user the 

 best of such means at his disposal. 



Practically, however, where the main object is thorough drain- 

 age, and not the clearing up of stone or brush (and in most cases, 

 even where such clearing is collaterally or contingently desirable) , 

 tile drains are superior to any other kind, because : — 



They cost less in the sum total of labor and material. 



They admit of being laid at flatter grades, and therefore of 

 draining larger areas of level lands to an outfall of limited depth. 



They are easily examined (through silt-wells), and imperfec- 

 tions or stoppages may be thus approximately located for repair 

 or removal. 



They are more durable, and, properly laid and cared for, are 

 practically permanent in their life and operation. 



There is a popular impression that ground water enters a tile 

 drain through the porous bodies of the tiles themselves. This is 

 essentially wrong. Indeed, the best tiles are those that are uni- 

 formly hard-burued to such a degree (just short of vitrification) 

 that nearly all physical porosity has disappeared. In point of 

 fact, at all times, excepting when the amount of water seeking to 

 enter a drain exceeds its maximum capacity when running full, the 

 water enters at the bottom of the joints and at the sides, as far up 

 only as the surface of the stream flowing in and through the drain. 

 One should not be tempted, therefore, to purchase tile for which 

 is claimed the virtue of admitting water through the porous mate- 

 rial comprising them, as such porosity serves no practical purpose, 

 and can result only from insuflicient burning, with consequent want 

 of durability. 



The joints of any laud tile (however accurately moulded, how- 

 ever well their shape may be retained in the process of burning, 

 and however closely fitted in laying) afford not only ample but 

 practically the sole means for the admission of water from the 

 soil around them. Indeed, the key to success in tile drainage, 

 after securing a suitable outfall and adequate grades leading down- 

 ward thereto, lies in making such close-fitting and well-protected 

 joints at the abutting ends of the tiles that clay and fine sand can- 

 not be carried into the drain by the water as it enters through the 

 joints. The subsoils of lands which best repay drainage are 



