Preparation of Soil by Drainage. 61 



cause of the ascent of the sap." In other words, too much water in the 

 soil may cause no marked difference between the underground climate of 

 winter and spring. 



Dr. Madden shows, moreover, that excess of water keeps out the air 

 essential not only in promoting chemical changes in the soil itself and 

 required by the plants, but also the air which is directly needed by the 

 roots. Sir H. Davy, and others, have proved that oxygen and carbonic 

 acid are absorbed by the roots as well as by the foliage, and these gases 

 can be brought to them by the air only. 



Again, drainage alters the currents which occur in wet soil. In 

 undrained land, evaporation is constantly bringing up to the roots the sour, 

 exhausted water of the subsoil, which is an injury rather than a benefit. 

 On the other hand, the rain just fallen passes freely through a drained 

 soil, carrying directly to the roots fresh air and stimulating gases. 



Wet land also produces conditions which disable the foliage of plants 

 from absorbing carbonic acid, thus greatly decreasing its atmospheric 

 supply of food. Other reasons might be given, but the reader who is not 

 satisfied had better set out an acre of strawberries on water-logged land. 

 His empty pocket will out-argue all the books. 



The construction of drains may be essential, for three causes. 1st. 

 Land that is dry enough naturally, may lie so as to collect and hold sur- 

 face water, which, accumulating with every rain and snow storm, at last 

 renders the soil sour and unproductive. 2d. Comparatively level land, 

 and even steep hill-sides, may be so full of springs as to render drains at 

 short intervals necessary. 3d. Streams, flowing perhaps from distant 

 sources, may find their natural channel across our grounds. If these 

 channels are obstructed or inadequate, we find our land falling into the 

 ways of an old soaker. 



It should here be stated, however, that if we could cause streams 

 to overflow our land in a shallow, sluggish current, so that a sediment 

 would be left on the surface after- a speedy subsidence, the result 

 would be in miniature like the overflow of the Nile in Egypt, most 

 beneficial, that is, if means for thorough subsequent drainage was provided. 



If there is an abundance of stone on one's place suitable for the con- 

 struction of drains, they can often be used to advantage, as I shall show ; 

 but for all ordinary purposes of drainage, round tile with collars are now 

 recommended by the best authorities. It is said that they are cheaper 

 than stone, even where the latter is right at hand ; and the claim is 

 reasonable, since, instead of the wide ditch required by stone, a narrow 

 cut will suffice for tile ; thus, a great saving is at once effected in the cost 



