AGRICULTURAL EXPERIMENT STATION. 



159 



1891, 



Depth of 

 TheiQiometer. 



Mean tempera- 

 ture for 7 mos., 

 April to Oct. 

 inclusive. 



Difference in 

 mean tem- 

 peratures. 



(Jlianges in tem- 

 perature for 

 one inch. 









56.65 

 56.89 

 55.56 

 54.74 

 54.52 

 52.49 

 51.36 







+0.24 

 -1.33 

 —0.82 

 —0.22 

 —2.03 

 —1.13 









4 0.12 





—0.44 





—0.27 





—0.07 





—0.17 





—0.09 









1892. 



Depth of 

 Thermometer. 



I Mean tempera- 

 ture for 7 mos., 

 April to Oct. 

 inclusive. 



Difference in 

 mean tem- 

 peratures. 



Changes in tem- 

 perature for 

 one inch. 



1 inch . . . . 

 3 inches. . 

 6 inches. . 

 9 inches . 

 12 inches. 

 24 inches • 

 36 inches 



55.62 

 .55.63 

 54.79 

 54.16 

 54.15 

 52.39 

 51.13 



+0.01 

 —0.84 

 —0.63 

 —0.01 

 —1.76 

 —1.26 



+0.003 



—0.28 



—0.21 



—0 003 



—0.14 



^0.10 



An examination of the tables shows that the soil responds 

 readily to the daily heat of the sun to the depth of three inches, 

 less readily to the depth of six inches, in a moderate degree only 

 to the depth of nine inches, and very slightly below twelve inches. 

 To the depth of three inches the range between the morning and 

 the midday observations has been as high as fifteen degrees. 

 The mean daily range at the depth of 1 inch during the period of 

 observations was 5°. 22 ; at the depth of three inches, 4°. 54 ; at 

 the depth 6 inches, 1°.81 ; at the depth of 9 inches, 1°,02, and 

 12 inches very slight. 



At the depth of 3 inches, the average temperature of the soil 

 was somewhat higher than at the depth of 1 inch. The surface 

 soil averaged about five degrees warmer than the soil 36 inches 

 below the surface. 



The rate of reduction of temperature with depth below the 

 layer three inches from the surface is shown in a general way in 

 the foregoing tables. 



This rate is probably in accordance with a simple law which can 

 be expressed by a mathematical formula, variable, undoubtedly, 

 for different soils. However, on examining the "changes in tem- 

 perature for one inch" in the foregoing tables, it will be noticed 



