206 



On the Physical Properties of Soil. 





In perfectly Fine Weather. 



In Variable Weather: Mean of the whole 

 Month. 



Months. 



Mean Temperature 

 of the 



>• to 



O fu cn 

 - i^Ci 1^ 



Mean Temperature. 







O 3 ^ OJ 



Of the 

 Earth's 

 Surface 

 at Noon. 



At three 

 Inches 

 below the 

 Soil. 









Earth's 

 Surface. 



Air in the 

 Shade. 



At four 

 Feet below 

 the Soil. 



Of the 

 Ail- in the 

 Shade, 



January . 

 February . 

 March . . 

 April , . 

 May . . 



July . . 



August 



September 



October 



November 



December 



. 0 , 



54.1 

 86.2 

 99.5 

 121.6 

 131.2 

 139.8 

 146.3 

 130.1 

 119.8 

 80.8 

 72.7 

 59.2 



^ 0 ^ 

 24.6 

 43.0 

 46.6 

 61.7 

 67.3 

 75.2 

 81.3 

 68.9 

 68.0 

 42.8 

 40.1 

 35.6 



29°. 5 

 43.2 

 52. 9 

 59^9 

 63 9 

 64.6 

 65.0 

 61.2 

 51.8 

 33.0 

 32.6 

 23.6 



0 



43.0 

 45.7 

 53.2 

 78.9 

 80.1 

 89.1 

 93.4 

 96.0 

 82.8 

 59.8 

 47.3 

 35.3 



o 



38.5 

 39.8 

 43.2 

 60.7 

 64.4 

 73.6 

 73.3 

 76.9 

 70.2 

 54.4 

 43.7 

 33.3 



39.4 

 38.6 

 38.1 

 48.3 

 54.6 

 61.5 

 64.9 

 68.6 

 66.1 

 58.8 

 49.0 

 39,0 



38.2 

 36.8 

 38.1 

 50.1 

 55.9 

 60.9 

 63.2 

 65.8 

 62.4 

 51.8 

 41.6 

 32.1 



Means . 



103.4 



54.6 



48.8 



67.1 



56.0 



52.3 



49.7 



The highest temperature occasioned by the mere heat of the 

 sun in the last two years^ I observed on the 16th of June, 1828 ; 

 the thermometer placed in the earth rose on that day at noon 

 (the wind being west, the weather calm and perfectly fine, and the 

 temperature of the air in the shade 78° F.) to 153J F., and there- 

 fore 75J° higher than in the shade; it attained to nearly the same 

 height on the 21st of June, on which day (with the temperature 

 of the air 84 and a brisk east wind) it rose to 151^°, and therefore 

 66 ° higher than in the shade ; on other days I remarked further 

 that when the weather was windy, while the temperature was the 

 same in the shade, the temperature of the earth in the sun rose 

 to a less elevation. The smallest difference I ever observed was 

 on the 11th of January, 1829, Vv^hen there was a brisk east wind ; 

 the temperature I obtained in the shade on that day was, even at 

 noon, 18° below the freezing-point, and the temperature of the 

 surface of the earth in the sun rose only to 6|° above the freezing- 

 point. The highest temperature observed in the Botanic Garden 

 at Geneva, in the years 1796 and 1797, in contact with the surface 

 of the earth, was 125°.4, which occurred on the 30th July, 1797 : — 



The highest, 3 inches deep below the surface 99°. 5 July 26—29, 1797 

 The highest, 4 feet deep below the surface 73°. 2 Aug. 1 — 4 „ 

 The lowest, 3 inches deep below the surface 23°. 0 Dec. 12 „ 



The lowest 4 feet deep below the surface 35°. sj^^'^' »> 



