0)1 the Draiiiage of Land. 



287 



should therefore be diverted from the surface either by open or 

 under-2:round drainage ; and the latter, as being the most effec- 

 tual, will in the long run be unquestionably found the cheapest. 



So various are the soils and situations of farms, and so many are 

 the gradations between the extremes of light absorbent sands or 

 gravels and cohesive clays, that no uniform system of drainage can 

 be applicable to them all. Our object is indeed rather to excite 

 attention to the subject than to offer instructions on the proper 

 mode for each, which would not only swell this brief notice into a 

 tedious essay, but would doubtless be also thought by those who are 

 professionally conversant with the subject to savour somewhat of 

 presumption. 



It may, however, be observed that those light loams, or sands 

 and gravels intermixed with a portion of pure clay, resting upon 

 beds of gravel, and which compose the true turnip soils," rarely 

 require draining ; but in those which consist of sandy and gravelly 

 strata, resting upon various kinds of clay (and comprising, per- 

 haps, the greatest portion of the arable land throughout the king- 

 dom), the water filters through them until it meets with the im- 

 penetrable layer by which its further progress is stopped. On this 

 layer the drains should be placed, and sunk into it just so far as 

 to allow a free passage for the water ; unless it should be very 

 near the top soil, in which case the drains must be sunk still 

 further down ; but if the soil be wholly clay, it will be useless to 

 sink them lower than sufficient to guard the materials v/ith which 

 they are covered from being injured by the tread of heavy cattle ; 

 or in arable land, from being disturbed by the action of the plough. 



It is obvious that the depth of drains, and their distance from 

 each other, must be governed by the nature of the soil. It is also 

 evident that " the flatter the surface, and the stiffer the soil, the 

 greater will be the number required;"* and the intermixture of 

 several different kiyers renders the drainage more complex and 

 difficult to manage than if the land consists simply of an upper 

 and an under stratum. Generally speaking, however, it is thought 

 that the object will in most cases be completely attained if the 

 main drains be carried to the depth of 30 inches to 3 feet, or at 

 the most to 3 J feet, the depth of the smaller drains, or tributary 

 feeders, being about 6 inches less. The main drains should be 

 cut deeper than the side ones, in order to prevent the water in 

 them from standing back when the main is full. It will also, in 

 most instances, he found more prudent to carry the main-drains 

 diagonally across the slope of any rising ground than to dig them 

 straight down the declivity, whereby a rapid fall is occasioned, 

 which is apt in heavy rains to sludge them up with earthy impu- 



* Penny Cyclopaedia. 



