4G4 THE HOME, FAKM AND BUSINESS CYCLOPAEDIA. 



we object to deep drains in clays, simply because the water will not get 

 down to them ; the objection applies eqally to shallow drainage. 



There can be no necessity for denying the fact, that neither shallow nor 

 deep drains will work well at the first in strong clays, if the surface has 

 been much wrought upon ; and that even in any case, deep drains will 

 not become effective quite so soon as shallow drains will. The pores and 

 interstices of the soil which have hitherto been filled with stagnant water 

 must be emptied, and the land acted upon both by frosts and drought, ere 

 the percolation is fairly begun. There are many cases in which the deep 

 drainer, applying his principles to the dense clays, is disappointed to find 

 the drainage less complete for a time than he had been led to expect. He 

 is consequently sorely tempted, at times, to come to the conclusion, that 

 deep drains will not work in the clays at all ; and he is, therefore, inclined 

 to revert to the shallow draining system. Now, there are several causes 

 why deep drains fail at first to lay clay soils quite so dry as they ought to 

 be. Perhaps they have been put in at a wet time of the season, and the 

 material filled in above the pipes being little elsQ than mud, it may be 

 years before the weather has much effect in making it become porous. 

 We have elsewhere pointed out the necessity for drains being formed 

 when the soil is tolerably dry ; but, if this cannot be attained, care should 

 at least be taken to keep the covering of as dry material as it is possible 

 to obtain. But the defective action of deep drains may also be the result 

 of unskilful management. The fact requires to be kept constantly in view, 

 that water cannot flow right and left towards the pipes on a truly hori- 

 zontal plane. It is along a sloping line that it must gravitate in the direc- 

 tion of the drain ; and, if the soil is very dense, the fall upon this line 

 must be greater than it would require to be in porous land. If we put in 

 drains at too wide intervals, these oblique water lines may come to the 

 surface without crossing or meeting each other, and hence the reason why, 

 in some cases, where the soil is imperfectly drained, a wet strip is seen half 

 way between the drains. It should also be remembered that land usually 

 subsides considerably after being drained, and consequently those which 

 are put in 4 feet deep this year, will not be more than 3 feet 8 inches 

 deep five years hence, and will, perhaps, be even 3 or 4 inches shallower 

 in other five years. This partly arises, no doubt, from the surface soil 

 being carried off by water, and by the crops that have been grown, but 

 the subsidence of the land is the main cause of the alteration. There may, 

 however, be another agency at work. Everyone knows that lime, and 

 other bodies that are heavier than soil, have a tendency to sink when 

 placed upon the surface. And if we apply the principle conversely, we 



