138 
On the Injluence of Water 
further consideration, and by reference to Schiibler s own experi- 
ments on the temperature of soils at Tiibingen and Geneva. 
At Tubingen his experiments were directed to the ascertain- 
ment of the mean highest temperature of the earth by a thermo- 
meter placed on its surface, — ■ 
" the bulb being covered only tV^^ of inch high with earth : these 
observations were recorded in perfectly fine weather, between noon 
and one o'clock, whenever the weather happened to be perfectly fine at 
that part of the day." 
It appeared that during the six hottest months, from April to 
September inclusive, the mean temperature of the surface wa§ 
181°. 4. Now it is evident that, if rain fell upon the earth when 
it was so highly heated, the surface must be cooled by it ; but it is 
equally evident that the substrata would be warmed; for the 
temperature of the atmosphere in the shade, which was also re- 
corded at the same hour, was 70°. 4 ; and that of rain, had it then 
fallen, would have been much the same. Thus, the rain, on 
reaching the earth, would acquire a temperature of about 100°, 
and communicate heat, as it descended, to the underlying portions 
of soil possessing a lower temperature. 
His experiments at Geneva, in 1796, give the mean heat of the 
soil on its surface — at 3 inches — and at 4 feet below it. The 
observations were taken every day, in all weathers, and there- 
fore, as described by the Professor, " in variable weather." The 
mean temperature, denoted during the corresponding six months 
of the year before-mentioned, was — 
On these results the author obsen'es : — 
" The elevation of temperature by the rays of the sun was, therefore, 
considerably less " (than at Tubingen), "according to the average re- 
sults of these observations, because the temperature of the upper surface 
of the earth on cloudy and rainy days often accords exactly with that of 
the air ; but, on the other hand, they give us more accurately the mean 
temperature of the ground at some depth." 
These experiments denote that, if the mean temperature of the 
rain, during the six months, accorded with that of the air, it 
would receive, on reaching the earth, an augmentation of thirteen 
and a half degrees of heat, and sink downwards at a temperature 
of 3°. 4 higher than that of the soil at 3 inches deep, and of 
13°. 2 higher than that of the soil at 4 feet below the surface; 
thus supplying at the same time heat and moisture to the under- 
lying soil. His tal)le also shows that, on the mean of the whole 
On the surface. 
At 3 inches below, . 
At 4 feet below, 
Temp, of air in the shade. . 
