90 EUROPEAN AGRICULTURE. 



which forms the principal watercourse, the condition of the 

 land is often such as to require submains, into which the side 

 or parallel drains empty themselves, and by which the water is 

 conveyed into the principal drain. This matter is so entirely 

 dependent upon the shape and situation of the land to be 

 drained, that no universal rule can be laid down. The number 

 of submains, and their position, must depend wholly upon the 

 shape and condition of the land to be drained; but the sub- 

 mains should be covered as well as the parallel drains which run 

 into them. 



The mains and the submains being completed, the next step 

 is to lay out the parallel drains : and the frequency of these 

 drains, or the distance which they should hold from each other, 

 depends upon the character of the subsoil. &quot; If,&quot; says Mr. 

 Smith, &quot; it consists of a stiff and strong till, or a dead sandy 

 clay, then the distance from drain to drain should not exceed 

 from 10 to 15 feet ; if a lighter and more porous subsoil, a dis 

 tance from 18 to 24 feet will be close enough ; and in very open 

 subsoils 40 feet distance may be sufficient. The drains,&quot; he 

 adds, &quot; should be run parallel to each other, and at regular dis 

 tances ; and should be carried throughout the whole field with 

 out reference to the wet or dry appearance of portions of the 

 field, as uniform and complete dryness is the object ; and portions 

 of the land, which may be considered dry in their natural state, 

 will appear wet when compared with those parts which have 

 been properly drained.&quot; 



Of the general form of the drains recommended by Mr. Smith, 

 I subjoin a sketch, (p. 91,) which will need no illustration. The 

 eye will at once discern the different forms which may be eligi 

 ble under different circumstances. 



The depth of the parallel drains should, according to Mr. 

 Smith, be at least two feet and a half, and he deems three feet 

 more eligible, so that the land may be subsoil-ploughed to the 

 depth of sixteen inches, arid the plough certainly should not pass 

 nearer to the drain than two inches ; that is, there should be at 

 least eighteen inches of workable soil above the stones with 

 which the drain is filled. A le^s depth, as far as injury to the 

 drain is concerned, might answer ; but experience has proved, 

 most strongly, that a much greater depth than this is to be pre 

 ferred for the perfect drainage of the land. The main drains and 



