DRAINAGE. 93 



The temperature of the soil, to the depth to which the 

 water is removed, is in a course of constant assimilation to 

 the temperature of the air at the surface. From this it 

 follows necessarily, that during that period of the year 

 when the temperature of air at the surface of the earth 

 is generally below 48, retentive soils which have been 

 drained are colder than those which have not. Perhaps 

 this is no disadvantage. In still more artificial cultivation 

 than the usual run of agriculture, gardeners are not insen- 

 sible to the advantage of a total suspension of vegetation 

 for a short period. In Britain we suffer, not from an 

 excess of cold in winter, but from a deficiency of warmth 

 in summer. Grapes and maize, to which our sombre skies 

 deny maturity, come to full perfection in many regions 

 whose winters are longer and more severe than ours. 

 However, we state the facts, without asking to put a large 

 amount therefrom to the credit of our drainage. A friend 

 of ours, who lived on the north side of a hill in a subalpine 

 district, did not see the sun for three months in the year. 

 He maintained that this was an advantage : that during 

 those three months the sun was worth nothing to any one : 

 whereas in summer he enjoyed the early beams of that 

 luminary for some hours before he appeared to his neigh- 

 bours on the south side of the hill, as well as his declining 

 rays after they had lost him. Perhaps our readers may 

 think that what we and our friend take by our respective 

 notions is much on a par. To a beautiful provision of 

 nature, by which, during seasons of excessive heat, summer 

 rains are made subservient to the double purpose of cool- 

 ing the arid surface and conveying warmth to the deeper 

 recesses of the soil, we can advert only cursorily, on account 

 of insufficient data. We have no satisfactory British ex- 

 periments with reference to the surface-heat of the earth. 

 Professor Leslie's only commence at 1 foot below the sur- 

 face. Schubler's experiments, made near Geneva, in the 

 year 1796, are strictly superficial. His thermometers were 

 sunk in the soil only to the depth of y^th of an inch. In 



