DRAINAGE. 



hurtful. Land may be drained so 

 much as to be deteriorated, as expe- 

 rience has shown. 



" When a single large and deep 

 drain will produce the desired effect, 

 it is much bettor than when there are 

 several smaller, as large drains are 

 more easily kept open, and last long- 

 er than smaller ; but this is only the 

 case in tapping main springs, for if 

 the water is diffused through the sur- 

 rounding soil, numerous small drains 

 are more effective : but as soon as 

 there is a sufficient body of water 

 collected, the smaller drains should 

 run into larger, and these into main 

 drains, which should all, as far as is 

 practicable, unite into one principal 

 outlet, by which means there will be 

 less chance of their being choked up. 

 "When the water springs into a drain 

 from below, it is best to fill up that 

 part of the drain which lies above 

 the stones or other materials which 

 form the channel, with solid earth 

 well pressed in, and made impervious 

 to within a few inches of the bottom 

 of the furrows in ploughed land, or 

 the sod in pastures ; because the 

 water running along the surface is 

 apt to carry loose earth with it, and 

 choke the drains. When the water 

 comes in by the sides of the drains, 

 loose stones or gravel, or any porous 

 material, should be laid in them to the 

 line where the water comes in, and a 

 little above it, over which the earth 

 may be rammed in tight, so as to al- 

 low the horses to walk over the drain 

 without sinking in. 



" It sometimes happens that the 

 water collected from springs, which 

 caused marshes and bogs below, by 

 being carried in new channels, may 

 be usefully employed in irrigating the 

 land which it rendered barren before ; 

 not only removing the cause of bar- 

 renness, but adding positive fertility. 

 In this case the lower ground must 

 have numerous drains in it, in order 

 that the water let on to irrigate it 

 may not stagnate upon it, but run off 

 after it has answered its purpose. 



" The third branch in the art of drain- 

 ing is the removal of water from imper- 

 vious soils which lie flat, or in hollows, 

 230 



where the water from rain, snow, or 

 dews, which cannot sink into the soil 

 on account of its impervious nature, 

 and which cannot be carried off by 

 , evaporation, runs along the surface 

 and stagnates in every depression. 

 This is by far the most expensive 

 operation, in consequence of the num- 

 b(!r of drains required to lay the sur- 

 face dry. It requires much skill and 

 j practice to lay out the drains so as 

 j to produce the greatest effect at the 

 least expense. There is often a layer 

 . of light earth immediately over a sub- 

 j stratum of clay, and after continued 

 rains this soil becomes filled with 

 water, like a sponge, and no healthy 

 vegetation can take place. In this 

 case numerous drains must be made 

 in the subsoU, and over the draining 

 tiles or bushes, which may be laid at 

 the bottom of the drains, loose gravel 

 or broken stones must be laid to with- 

 in a foot of the surface, so that the 

 plough shall not reach them. The 

 water will gradually sink into these 

 drains and be carried off, and the 

 loose wet soil will become firm and 

 dry. In no case is the advantage of 

 draining more immediately apparent. 

 The average depth is 30 inches. 



" It is very seldom that a field is ab- 

 solutely level ; the first thing, there- 

 fore, to be ascertained is the greatest 

 inclination and its direction. For this 

 purpose, there is an instrument essen- 

 tial to a drainer, with which an accu- 

 rately horizontal line can be ascer- 

 tained, by means of a plummet, a 

 bricklayer's level, or a spirit level. 

 A sutEcient fall may thus be found or 

 artificially made in the drains to car- 

 ry off the water. The next object 

 is to arrange drains so that each 

 shall collect as much of the water in 

 the soil as possible. Large drains, 

 except as main drains, are inadmis- 

 sible. The depth should be such 

 only that the plough may not reach it, 

 if the land is arable, or the feet of 

 cattle tread it in, if it be in pasture. 

 All the drains which are to collect 

 the water should he as nearly at 

 right angles to the inclination of the 

 surface as is consistent with a suffi- 

 cient fall in the drains to make them 



