REMARKS ON DRAINING 



115 



frequently on the same estate, grounds may be found on which 

 the crops suffer from both extremes, although each portion 

 receives equal, or very nearly equal, quantities of rain. The 

 owner of such lands cannot, of course, prevent the rain from 

 falling on the wet as well as on the too dry grounds ; but in nine 

 cases out of ten, or perhaps ninety-nine in a hundred, the rain 

 which falls may be economized to the benefit of the crops on 

 dry ground, and the excess of moisture may be drained off, so as 

 not to be injurious to those in ground naturally too wet. 



In draining land the condition of the adjoining higher grounds 

 ought to be the first consideration. If they too rapidly part 

 with their moisture, tending thereby to inundate the lower 

 ground, whilst they soon after suffer from drought, that, should, 

 if possible, be prevented. Trenching will afford greater depth 

 of soil for absorption, and consequent detention of moisture, till 

 the time of need — till the growing crops require it to supply 

 their evaporation ; and on such high ground, if moisture is pre- 

 sent, the crops will evaporate a vast quantity: thus so much 

 moisture will be most advantageously intercepted for the neces- 

 sary supply of the crops where it falls, and also be prevented 

 becoming injurious to those on lower ground, where it is not 

 wanted, and from which it would consequently require to be 

 drained off. 



The proportion which evaporation from various surfaces bears 

 to the quantity of rain which falls, has not been sufficiently 

 investigated to enable us to form any very correct estimate : 

 that from a surface of water has, however, been found to be 

 more than the amount of rain ; that from earth much less ; and 

 a tree with a large mass of foliage requires more moisture than 

 falls on the space of ground it covers. When the surface of the 

 ground is dry, the evaporation from it is almost nothing ; but the 

 surface may be dry and yet much moisture, if it exists below, 

 may be drawn up and carried off by evaporation from the leaves 

 of growing crops. Thin land is soon saturated by heavy rains ; 

 saturation is an evil which, in this case, is often remedied by 

 drawing surface-furrows, along which the rain-water is readily 

 carried off, without its being remembered that probably in less 

 than six weeks that water would be required to feed the crops 

 growing where it fell. In the generality of cases, I believe, it 

 will be found that none of the rain which falls on ground sloping 

 to the south should be carried off by the surface. Snow-water 

 may be drained off with propriety as quickly as possible from 

 the north sides of hills, but in all cases the summer rains should 

 be permitted to sink through the ground. 



This detention of water may be looked upon as the opposite 

 of draining, and therefore foreign to the latter subject. These 



