94 THE PRINCIPLES OF 



In the first place, I should say that by drainage we get rid 

 of stagnant water. That is the great advantage in drainage. 

 It is not that we get rid of water, but that we get rid of 

 stagnant or effete water. Stagnant water is exhausted of 

 its oxygen by contact with decaying vegetable matter. It 

 has therefore become soured. In the next place, it keeps out 

 fresh supplies of water. It is leading a sort of dog-in-the- 

 manger existence useless itself, effete itself, and at the same 

 time preventing the accession of fresh water. 



Now if we can rid land of stagnant water, if we can so 

 manage as to allow a free passage of water through the soil, 

 we make way for fresh water, and that fresh water is thoroughly 

 aerated. It likewise contains those stores of nourishment 

 which rain-water brings down from the atmosphere. It 

 contains a certain proportion of carbonic acid gas. It contains 

 nitrogen, it contains ammonia, and also a very considerable 

 portion of chlorine in the form of common salt. This water 

 is brought into close contact with the growing roots, and 

 then passes onward. The fact that the water is in a state 

 of movement that it ceases to be stagnant is a perfect 

 guarantee that it is accompanied with and followed by air, 

 so that the soil becomes oxidized. The iron salts in the soil 

 are maintained in a perfect state of oxidation. The vegetable 

 products in the soil are converted into available plant food. 

 All the numerous benefits which a free accession of air into 

 the soil can give are in this way obtained. 



In the next place drainage has produced an alternation of 

 condition from wet to dry and from dry to wet ; whereas an 

 undrained soil is always in a water-logged condition. The 

 drained soil is alternately wet and dry, while in the tin- 

 drained condition it is in a constant state of wetness. The 

 consequence of these alternations is pulverization of the soil, 

 and this pulverization is carried to a very considerable depth, 

 so that clay soils which have been subjected to the operation 



