4 
The Effect of Climate and Weather on the Soil. 
deep, uniform in texture, and free from stones ; they are easily 
worked and very fertile where the water supply is good. 
The loess soils represent the simplest case because they are 
formed by the sorting action of the wind, there has not been 
much change in transit. Other modes of carriage involve greater 
change : thus ice in some cases has ground the particles down 
considerably and the final result of the glacier action and 
subsequent changes has been to produce a great deal ot boulder 
clay of no very high agricultural repute. 
Thus we see that the mineral part of the soil is very 
considerably affected by the climatic conditions that have 
obtained since the original rock began to split up. The effect 
has been produced in two directions : in determining the way 
in which the particles have broken down, and in determining 
the extent to which they have been removed or sorted out 
since. In both ways the character of the soil is altered. 
Sometimes the climate has changed, but it always leaves its 
mark. Over the part of Great Britain which is covered with 
glacial drift the character of the subsoil is determined by a 
climate that has long since vanished, while the surface soil has 
been modified by the climate we now enjoy. 
We must now turn to a third highly important effect or 
climate on soil, viz., its effect on the organic matter of the soil. 
The Influence of Climate on the Organic 
Matter of the Soil. 
The mass of mineral particles formed by the weathering of 
the rocks and the sorting out by subsequent agencies is not yet 
soil, although it may be looked upon as the framework of the 
soil! But it soon covers itself with vegetation which gradually 
has a most profound effect and converts the mineral, mass into 
a true soil. As this vegetation dies its residues mingle with 
the mineral particles, being carried in by earthworms and 
various insects. During its lifetime the plant has been making 
a good deal of the substance of its leaves and stems from the 
gases of the air and the rain water, and the materials thus 
formed contain stored up energy derived from the sunlight. 
When they mingle with the soil and begin to decay the energy 
is liberated in the form of heat, and by the time they are 
completely decayed they have given out just as much heat as if 
they had been burned in a bonfire. The original heap of 
mineral matter contained no easily available stores of energy ; 
the mixture of mineral matter and plant residues on the other 
hand does. The consequence of this addition is very pro- 
found ; life is now possible in the soil, and there springs up a 
vast population of living creatures all drawing on this 
accumulated store of energy, flourishing so long as it holds out 
