112 ON DRAINING. 



course; left at the proper places for the parallel drains t 

 enter. Their heiglit is commonly 9 inches, the distance 

 apart about 7 inches ; and they are surmounted by strong" 

 flag'-stones or '^ covers," any interstices between which 

 are carefully filled up with small stones, to prevent the 

 entrance of earthy matters. There is thus formed a con- 

 duit, or "eye," as it is here designated, of 7 inches in 

 width by 9 in height, which is capable of voiding- a con- 

 siderable body of water. When the subsoil is composed of 

 sand, or is in any degTee soft, the bottom of the main-drain 

 is generally paved with round stones, previous to the for- 

 mation of the little side walls of the conduit, with the view 

 of insuring the permanency of the work. Indeed, many intel- 

 lig'ent agriculturists are of opinion that whatever may be 

 the texture of the subsoil, the bottom of all mains should be 

 so paved, as, however firm and secure it may be at the time, 

 there is some reason to apprehend that the continual abrasion 

 of the water would eventually undermine the sides, or other- 

 wise endang-er the safety of the drain. No doubt the cost 

 is thereby increased ; but, in the opinion of many skilful 

 drainers, it is an exceedingly false economy to construct 

 main drains in an imperfect or insecure manner, for the sake 

 of saving a trifle of the expense. Efficiency and durability 

 are the great points to be aimed at in their formation ; and 

 the judicious farmer will not hesitate to incur a little addi- 

 tional expense, in order to secure these desirable qualities ; 

 especially when aided, as he always should be, by his land- 

 lord. There are various other sorts of main drains besides 

 that just described ; but, as neither of them is so much 

 approved of as it, it is deemed unnecessary to occupy 

 valuable space with any further remarks on this part of our 

 subject. 



Common Drains. — The parallel or common drains are in- 

 variably made in the direction of the greatest ascent or slope 

 of the gTound, except where it is considered the declivity is 

 so great that the velocity required by the water in descend- 

 ing, Avould be likely to produce an injurious effect ; in which 

 case it is supposed by some to be necessary to direct them 

 with a slight inclination across the slope, in order to diminish 

 the force of the current of water in the drain. But it is, 

 perhaps, needless to observe that such situations rarely stand 

 in need of thorough-draining-, at least not in such a degree 

 as the low and almost flat g-rounds, which it is the farmer's 

 fijt'st care to relieve of redundant moisture. 



