GROUND OPERATIONS. 



143 



draining their way, Kterally paddling their own 

 canoe towards finding their own level in obedience 

 to that mightiest of all water-disturbing and dis- 

 tributing forces, the law of gravitation, it would be 

 found that the silver matched, if it did not over- 

 master, the verdure. 



The major part of this water, so much of it in- 

 deed that the word "all" might fairly be used, is 

 like Tennyson's brook, flowing on and on for ever. 

 And the main object of all this stupendous ma- 

 chinery in motion is to lay the land dry. 



The land becomes wet from two sources. The 

 overflow water from higher elevations sweeps down 

 over the surface, and floods that of a lower level. 

 Or, more generally, and in far larger quantities, it is 

 absorbed by the surface, temporarily stored in the 

 soil or subsoil, conveyed through flssures in the 

 strata, and comes forth sometimes near to its source, 

 at others at great distances from it, in lower springs. 

 In these cases the water is said to rise from below, 

 and it does so frequently to such an extent that the 

 whole of the subsoil, and then the surface, thus 

 becomes soured or saturated. 



The first point in successful drainage, therefore, 

 consists in cutting off these subterranean supplies, 

 or, if that cannot be done, the caiTying away of this 

 foreign excess of water by drainage. In cases where 

 the causes and source of this water can be traced, one 

 main drain may often become almost sufficient to 

 drain an entire field or garden. (See Fig. 11.) Fre- 

 quently, when this foreign water is removed, the 

 rainfall will not be found to be excessive. 



Much win be found to depend upon the rainfall 

 of the locality, and this varies as widely as from 

 twenty to forty inches a year. The character of the 

 soil and subsoil must also be taken into account. It 

 is well, however, to test the matter by time, by the 

 incline of the strata, &o. If the character of the soil 

 and subsoil, and especially the conduct of the newly, 

 made main drain by its fall and constant discharge, 

 point to spring-water as the cause of the excessive 

 wetness of the land, it will be wise to test the result 

 by experience before going to the expense of drain- 

 ing off the surface or rain water. By one or both 

 methods the drainage must be made so perfect as to 

 dry the land sufficiently for cultural purposes. 



As gardens caimot well be drained after they are 

 formed without a heavy sacrifice of money and 

 material, it is important to drain the ground before 

 making them, and in all cases to give the drainage 

 the benefit of any doubt that may exist about its 

 necessity. Were the mere removal of the excess of 

 water the one and only merit of drainage, this 

 might be of less moment. But it is very nearly 

 otherwise, and this leads to the second branch of the 

 subject. 



Drainage also Keeps Iiand Moist. — 



Drainage, by removing the excess, husbands a 

 sufficiency of water ; and m the case of garden soils, 

 enough water is far better than a feast, that is, a 

 flood. Any one at all conversant with the effects of 

 drought on wet soils, must have observed that the 

 merest mud of a month or so before is the very first 

 soil to become as hard as brickbats under the dry- 

 baking of a severe drought. So hard indeed does the 

 wetsoU become, that it rends into fragments and deep 

 fissm-es rather than yield in the mass to the contract- 

 ing powers of the drought. The mud of yesterday 

 becomes the impracticable lumps and vmbreakable 

 clods of to-day, and as long as the drought lasts. 



■|?;^?^. 



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Fig. 11. — Drain at B, intercepting water delivered by falling 

 strata from liiglier levels at a and b. 



Nor are these drying effects merely seen in the 

 mechanical behaviour or condition of wet lands under 

 drought, but the crops are also the first to suffer, and 

 to hoist unmistakable signs of distress on wet lands. 

 Such lands are, in fact, the victims of unequal distri- 

 bution. The drowned land of one month becomes 

 the baked, parched land of the next, and so on and 

 on continually until the drainer's spade and material 

 set the water on a downward track, and thus dis- 

 tribute it equally all through the mass of earth. 

 The passage of the water into deeper tilths moves it 

 from the influence of wasteful dissipation by the sun 

 and dry air. Every drop of water absorbed also so 

 alters the character of the surface and substance of 

 the earth as to make it more difficult for sun and 

 wind to reach it. 



Each drop of water, digging its own way to the 

 drains, blocks the passage behind it with- one or 

 more .molecules of air, thus making the soil porous, 

 and within reasonable limits the more porous the 

 earth the more moist, for air is one of the most 

 powerful resistors of either heat, cold, or drought. 

 Hence, while wet land may be sun-baked to a depth 

 of several inches, properly drained loose-surfaced land 

 may not be dried half an inch, and is seldom or never 

 baked into hardness at all under the severest drought. 



Besides, as the whole of the excess of water in 

 undrained lands has to be lifted from the surface by 



