100 AGRICULTURE. 



some inches deeper than 4 feet. If the land lies on a 

 slope (say 4 inches to the yard), drains of 4 feet, if driven 

 on the line of steepest descent, will effect the object ; be- 

 cause, though water at 4 feet, lying at the intermediate 

 point between two drains, in a line at right angles to them, 

 cannot for want of fall get into either of them by travelling 

 6 yards, it will find a fall of 4 inches at less than 7, and 

 of 8 inches at less than 8, yards. If we must speak quite 

 correctly, this intermediate water will never get into the 

 drain till there is a fresh supply ; it will descend perpen- 

 dicularly, pushing out that which lies below it, and will be 

 itself displaced by a fresh arrival from the heavens. In 

 order that the whole soil, if homogeneous, or nearly so, 

 may be drained evenly, it is manifest that the drains must 

 be parallel. Extra friction in the soil must be met either 

 by making the drains deeper, or by placing them nearer. 

 On this point, which is one of practice rather than of prin- 

 ciple, each case must be left to the sagacity of the operator. 

 We doubt whether in any natural soil the friction is so 

 great as to resist a fall of 1 inch in a yard. If we are 

 right in this point, we should always attain the object of 

 lowering the water-table to 4 feet by 4-feet 6-inch drains, 

 parallel, and 12 yards apart. We have already stated one 

 advantage which results on a slope from driving the paral- 

 lel drains in the line of steepest descent: to wit, that 

 when they are so driven, all water which lies at the same 

 depth from the surface as the bottoms of the drains, can 

 find a fall into one or the other by travelling a little more 

 than half the distance between them ; whereas, if the 

 drains are driven across the slope, half the water so situated 

 as to depth can only find a fall into the lower drain, and 

 in order to reach it must travel distances varying from 

 one-half to the full interval between the two. Smith, of 

 Deanston, stated one reason for the steep course, namely, 

 that on slopes alternate horizontal beds of porous and 

 retentive soil frequently cropped out; that the water 

 issuing from the lower edge of the porous runs over the 



