on the Temperature of Soils. 
139 
rear, the increase of temperature imparted to the soil by the rain 
would have been 2°. 4 at 3 inches, and 6°.l at 4 feet deep, 
Schiibler's remark, therefore, " that the earth in hot weather be- 
comes rather cooled than otherwise " by rain, is only applicable to 
the effect produced on its superficies, which is there beneficial. 
The section of this author's Treatise on the " Influence of 
Moisture on the Warming of Soils" must be deemed incomplete, 
by reason of the absence of all reference to the warming effect of 
dew : which — whether it be considered as directly communicating 
heat to the surface of soil necessarily colder than itself at the time 
of its precipitation, or as diminishing to a great extent the radia- 
tion of heat from the earth to the heavens — is an agent which 
performs an energetic part in maintaining a sufficiency both of 
heat and moisture in the mass of the soil. 
Leslie's Experiments. — In the Supplement to the 'Encyclo- 
paedia Britannica,' Art. Climate, written by Professor Leslie, will 
be found a table of experiments on the temperature of the earth, 
for each month of the years 1816 and 1817, at four different depths, 
viz. 1, 2, 4. and 8 feet below the surface. They were made at the 
instance of Mr. Ferguson of Raith. It is stated that the instru- 
ments were sunk in a soft gravelly soil, which turns, at 4 feet 
below the surface, into quicksand, or a bed of sand and water.'' 
As it does not appear that these experiments were conducted with 
any other intent than to assist Leslie in some deductions relative 
to isothermal lines, and to the correspondence which might subsist 
between the mean annual atmospheric temperature of a given 
parallel of latitude, with that of springs and of the earth at certain 
depths, I have thought it unnecessary to extract the Table. Such 
deductions are, at best, very vague, nor are they calculated, in the 
slightest degree, to illustrate the physical properties of the various 
soils which form the crust of our globe, and which come within 
the province of the farmer ; neither can they serve to assist his 
judgment in the management of them. The mere determination 
of the heat of the earth " at depths accessible to the cultivator" is 
useless, unless the observations be so conducted and recorded as 
to lead to the discovery of the circumstances which influence its 
temperature. I had the advantage of passing several days, about 
20 years since, in company with Leslie, at the house of the late 
Lord Rosslyn in Fifeshire, and he took me to Mr. Ferguson's of 
Raith. to show me the thermometers in the ground. They were 
then, if I recollect right, two in number, and sunk in grass-land, 
the one descending 12 inches, the other 36 inches below the sur- 
face. Leslie's mind was, at this time, so pre-occupied with his 
newly invented instruments, the photometer, differential thermo- 
meter, hygrometer, &c. — with which his hands and his pockets 
were filled — that I was unable to engage his attention, seriously. 
