148 



MAINE STATE COLLEGE 



1890. 



Depth of 

 Thermometer. 



1 inch 



3 inches- . 

 6 inches. ■ 

 9 inches- . 

 12 inches. 

 24 inches. 

 36 inches. 



Mean tempera- 

 ture for seven 

 months. April to 

 Oct. inclusive. 



54.63 

 54.92 

 53.96 

 53.26 

 53.31 

 51.96 

 50.77 



Difference in 

 mean tempera- 

 ture. 



-4-0.29 

 —0.96 

 —0 70 

 •4-0.05 

 —1.35 

 —1.19 



Changes in tem- 

 perature for one 

 inch. 



-M3.14 

 —0.32 

 —0.23 

 +0.02 

 —0.11 

 -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°. 62 ; at the depth of three inches, 5°. 26 ; at the 

 depth 6 inches, 1°.90 ; at the depth of 9 inches, 1°.18, and below 

 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 clearly shown in the foregoing 

 tables. 



Comparing soil temperatures with air temperatures during the 

 two seasons under notice, the following mean results appear. 

 At the depth of 1 inch, the temperature of the soil was lower 

 than that of the air by 2°. 40 ; at the depth of 3 inches, by 2°. 11 ; 

 6 inches, by 3°.16; 9 inches, by 3°,94 ; 12 inches, by 4°.18 ; 24 

 inches, by 5°. 78, and at the depth of 36 inches, by 7°. 18. 



Terrestrial Radiation. 



The heat ladiated from the surface of the earth during the 

 night reduces its temperature several degrees below that of the 

 surrounding atmosphere. The amount of this radiation or the 

 consequent reduction of temperature is approximately shown by 

 comparing the readings of a terrestrial radiation thermometer 



