Chapter III. 
THE TEMPERATURE OF THE SOIL. 
OBSERVATIONS AT HOUGHTON FARM AND GENEVA, N. Y., BY 
D. P. PENHALLOW. 
In reference to the value of soil temperatures, Penhallow states 
(Aer. Se.,-Vol. I, p..(8) : 
A proper knowledge of the temperature of the soil must serve to 
guide us in reference to the time of planting particular seeds and the 
depth at which they should be planted, as determined by the condition 
and character of the soil. When the farmer gently packs the earth 
over the planted seed he derives a measure of benefit in the higher 
temperature of the soil at that place, whereby germination is accel- 
erated. Similarly, we can understand that cultivation during periods 
of excessive heat must tend to avert some of the evil results otherwise 
following from an excess of temperature. Moreover, in seasons of 
great or even of ordinary dryness a judicious system of irrigation 
must be of the greatest aayintaae not only as supplying needed fluids 
for the general functions of growth, but as reducing the otherwise 
high temperature of the soil toa degree that is well w ithin the danger 
limit and consistent with normal growth. 
Penhallow also shows from observations at Houghton Farm and at 
Geneva, N. Y., that all layers of the soil within 3 inches of the surface 
have temperatures that depend not merely upon absorption of solar 
heat but also upon the cooling due to radiation and evaporation. 
The depression due to evaporation amounts to about 8° C. on the 
average of the warmer half of the year and is even more than this 
when hot days and strong dry winds produce an excessive evaporation. 
OBSERVATIONS BY E. S. GOFF. 
S. Goff adduces observations to show that the temperature of the 
water at the time when it enters into the roots from the soil has some 
relation to the temperature of the stem of the plant for a short 
distance above the surface soil, and that the distance up the stem to 
which this temperature is felt depends upon the rapidity of the flow 
of the sap, and therefore ultimately on the rapidity of transpiration 
from the leaves. (Agr. Sci., Vol. I, p. 134.) 
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