550 Transactions of the American Institute. 



essential to his complete success. Cultivated lands, like human 

 heinous, have absolute wants. Our soils, as well as we ourselves, 

 need light, air and warmth. In general, our fields are made less 

 fruitful by drenching than by drouth. The presence of water in 

 the surface soil drives off heat and excludes the air. In homoge- 

 neous soils there can be no question as to the benefit of deep 

 plowing. The greater the surface exposed, the greater will be the 

 amount of air absorbed. Every shower prepares the soil for a 

 fresh supply of air. It is not improbable that in many cases deep 

 plowing will preclude the necessity of under-draining. The main 

 benefit of judicious drainage is the elevation of the temperature of 

 the land, for, in many kinds of soil, warmth is more important than 

 moisture. The surplus store of water, deep in the ground, is car- 

 ried up by capillary attraction, as the surface soil becomes dry 

 during the warmer months; but when this supply is greater than 

 is needed, the excess of evaporation tends to lower the tempera- 

 ture of the soil. Several years ago, the Marquis of Tweeddale 

 caused experiments to be made to ascertain the precise effects of 

 drainage on the temperature of the same kind of soil growing the 

 same crops. It was shown thereby that, except in midsummer, 

 when increased heat is not needed, the effect of drainage was to 

 increase the mean temperature of the soil at the depth of thirty 

 inches below the surface about one degree and a half. That 

 showers of cold rain and sleet lowered the temperature of drained 

 land two degrees, and undrained four degrees. Dr. Madden found 

 that an excess of water in the soil reduced its temperature six and 

 a half degrees, which he estimates is equivalent to an elevation 

 above the sea level of nearly two thousand feet. Two fields, side 

 by side, and equally well cultivated, one only being properly 

 drained and the other undrained, would show a great difference in 

 product. The undrained field would produce no more than a 

 drained field at an altitude two thousand feet higher. Further- 

 more, he calculates that one hundred cubic inches of moderately 

 pulverized soil contains twenty-five cubic inches of air. Every acre 

 cultivated to the depth of eight inches will, therefore, retain 

 12.545,280 inches of air, and for every additional inch cultivated 

 by deeper plowing, two hundred and thirty-five tons of soil are 

 brought into activity, and rendered capable of retaining within it 

 1,568,160 additional cubic inches of air. The lateness of the hour 

 prevents further discussion of this subject to-day, but I hope it 

 will again be taken up. 



