OH the Temperature of Soils. 
129 
Gain of moisture 
in an hour. 
Grains. 
" 1000 grains of a celebrated soil from Ormistown, in 
East Lothian . . . . . .18 
1000 grains of a very fertile soil from the banks of 
the river Parrett, in Somersetshire . .16 
1000 grains of a soil from Mersea, in Essex . .13 
1000 grains of a fine sand from Essex . .11 
1000 grains of a coarse sand . ... 8 
1000 grains of a soil from Bagshot Heath . . 3 " 
In reflecting on the results of these isolated experiments, and 
on the conclusions drawn from the consideration of some single 
property of soils (whether they be just or otherwise), the philo- 
sophic mi«d cannot fail to perceive how infinitely more valuable 
such experiments would be to the agriculturist were they com- 
bined with direct indications of the actual constitution of the same 
soils in their natural state, and under culture, as regards their 
attraction for heat and moisture. May it not be reasonably ex- 
pected that a well-conducted series of experiments on these phe- 
nomena would illustrate some of the causes which conduce to 
render certain soils in a higher latitude more productive than 
others in a more southern one ? Might they not serve to detect 
fallacies in reasoning or practice — to show, possibly, that effects 
have been attributed to wrong causes — and to unfold to our per- 
ception a clearer and more correct knowledge of the workings of 
natJire ? 
From the foregoing review of the physical properties of soils, 
in relation to heat and moisture, and of the action of water in 
warming or cooling them, it will be seen that a very remarkable 
difference obtains between the properties of the fluid and solid 
bodies. It appears that water absorbs heat rapidly, but can only 
convey it downwards by itself descending into the earth ; that 
the heat which it receives from the solar rays is again projected 
into the atmosphere by radiation, and in combination with vapour, 
when it remains stagnant on or near to the surface ; whereas, 
solid substances impart the heat which they absorb to all sur- 
rounding matter, in all directions (though with different de- 
grees of rapidity), as well as to the atmosphere. There is yet 
another important effect arising from the radiating force of solids 
to notice. As the sun verges towards the horizon, the superficial 
layer of the earth becomes colder than the atmosphere, causing 
the precipitation of dew, which the affinity of earthy matters to 
moisture enables them to absorb, and thereby to recruit in part, 
by night, the loss of moisture which has taken place during the 
day. Water also radiates heat powerfully, but it does not attract 
moisture to itself, except under very peculiar and rare circum- 
VOL. v. K 
