70 Grafting, 



illustrated in Fig. 35. Round tiles are apt to become filled 

 and clogged by the roots of trees and shrubs ; they are 

 best used in open places, where they are in no danger of 

 being rendered useless. 



On land with a stiff and clayey subsoil, drainage is a 

 most important operation which must receive special atten- 

 tion. If the area to be drained is large arid a number of 

 trenches must be dug, a main drain with an easy flow to 

 some large, open ditch or river is constructed. With this 

 all the lateral drains are connected. Such drains should 

 unite with the main drain at an acute angle, and can be 

 from twenty-five to fifty feet apart, or more, according 

 to the need of the ground. Ordinarily, a main drain of 

 round tiles from four to six inches in diameter, will carry 

 off all the superfluous water of several acres. For lateral 

 drains the one and a half or two-inch size is sufficient. 

 Round tiles when laid are put end to end, but not joined. 

 A minimum fall of six inches in one hundred feet is neces- 

 sary, and may be had on the most level ground. No drain 

 should be nearer the surface than three feet. Hence if the 

 ground is almost level, as most watery land is apt to be, the 

 drains at their outlet must be several feet deeper than at the 

 other end. For instance, in digging a drain six hundred 

 feet long on flat land, it is necessary, in order to ensure the 

 proper fall of six inches in a hundred feet, to make it six 

 feet deep at its outlet, while at its opposite end it is only 

 three feet deep. In a garden, larger and deeper drains, and 

 a greater fall is needed than in an open field. If the drains 

 are made very shallow, a greater number are needed to 

 drain a given piece of land. The depth and distance must 



