192 HOW CROPS FEED. 



eter placed at a depth of a little more than one inch, gave 



these results: 



In quartz sand 126* 



In crystalliue lime soil 115° 



In j!farflen soil 114° 



In yellow sandy cluy 100° 



In pipe clay 94° 



In chalk soil 87* 



Here we observe a difference of nearly 40° in the noon- 

 day temperature of the coarse quartz and the chalk soil. 

 Malaguti and Durochcr found that the temperature of the 

 garden soil, just below the surface, was, on the average 

 of day and night together, 6° Fahrenheit higher than that 

 of the air, but that this higher temperature diminished at 

 a greater depth. A thermometer buried four inches indi- 

 cated a mean temperature only 3° above that of the at- 

 mosphere. 



The experimenters do not mention the influence of wa- 

 ter in affecting these results ; they do not state the degree 

 of dryness of these soils. It will be seen, however, that 

 the warmest soils are those that retain least water, and 

 doubtless something of the slowness with which the fine 

 soils increase in warmth is connected with the fact that 

 they retain much water, which, in evaporating, appropri- 

 ates and renders latent a large quantity of heat. 



The chalk soil is seen to be the coolest of all, its tem- 

 perature in these observations being three degrees lower 

 than that of the atmosphere at noonday. In hot climates 

 this coolness is sometimes of gfeat advantage, as appears 

 to happen in Spain, near Cadiz, where the Sherry vine- 

 yards flourish. " The Don said the Sherry wine district 

 was very small, not more than twelve miles square. The 

 Sherry grape grew only on certain low, chalky hills, where 

 the earth being light-colored, is not so much burnt ; did 

 not chap and split so much by the sun as darker and 

 heavier soils do. A mile beyond these hills the grape de- 

 teriorates." — (Dickens' Household Words Nov. 13, 1858.) 



