12G UXDERDRAINING AND DEEP TILLAGE. 



is a cooling process, has been used by Provideftce to minister to our 

 comfort in the summer time. By the evaporation of the moisture of 

 perspiration on our foreheads, a refreshing coolness is given, ■which 

 otherwise could not have been obtained, except by a reduction of the 

 temperature around us. A more convincing proof of the truth can 

 be obtained by personal experiment. Let one stand wiih damp 

 clothes in a draft of air, and the chilliness immediately consequent 

 upon the exposure is proof positive. Now the same holds true of 

 the water at the surface of undrained land. By the evaporation 

 of the moisture which cannot be di.sposed of in any other way, the 

 ground is cooled by just as many degrees as are required to change 

 water from its liquid to its aeriform state. Of course but rude 

 guesses can be made in relation to the actual amount lost by this 

 means, but the best authorities declare that the diminution amounts 

 to at least 9*^ or lO'^ Fahrenheit. And this number of degrees of 

 heat could be saved to the land by the avoidance of evaporation. 

 Draining does this by taking away the superfluous water and allow- 

 ing only a due quantity of moisture to remain in the soil. Thus as 

 we have seen, the soil, by draining, gains warmth both in a posi- 

 tive and negative manner, positivelij^ by bringing surface heat 

 where it can be retained and used ; negatively, by preventing loss 

 of heat hy diminishing the evaporation. 



Next, I mention the advantage gained by the farmer in being 

 enabled to work the soil earlier in the spring, and much sooner after 

 heavy rains, at any season, than otherwise could be the case. As 

 we have just seen, draining keeps on hand the requisite amount of 

 water in the soil, and no more than the right amount. So that 

 when the melting of the snow in spring has left a superabundance 

 of water on the surface, the underdrains carry it ofT readily. And 

 whenever in spring, summer or autumn, after a long storm, the 

 drenched soil is rendered heavy by the great amount of water con- 

 tained in it, it is relieved of this surplus moisture by the drains; 

 while without them the ground would be cooling from evaporation 

 of the surface water and much warmth would be wasted ; wiili them 

 the ground is left moist but not soaked — it is soon ready to work. 

 This on clays and clayey loams, is of great account, as from their 

 adhesive nature, they require to be worked at just the right time in 

 spring because they otherwise become clodded and baked. But, by 



