26 
TRANSACTIONS OP THE TEXAS ACADEMY OP SCIENCE. 
rational method of tillage, and it is then, if it be properly presented, that 
he comes to appreciate the assistance which may be given him by the 
geologist and the agricultural chemist. 
For the purpose of ascertaining the value of any soil, the crops to 
which it is best adapted, the best means of maintaining or increasing its 
fertility, or its amelioration if necessary, the farmer considers its appear¬ 
ance, the plant growth he finds on it, and the results obtained by actual 
cropping and experience. The geologist takes it up differently. He 
seeks to ascertain the origin of the soil, the manner of its formation, the 
character of the materials composing it, both as to their chemical compo¬ 
sition and physical condition, the local supplies of suitable fertilizers, 
the conditions of water supply, of irrigation and of drainage. He also 
notes the character of the existing plant growth, and from the results of 
these studies decides upon the true character and utility of the soil. 
These facts, whether they be gathered by the trained geologist or dug 
out by the more laborious and often uncertain methods of the farmer, 
are those on which rational agriculture must depend. The farmer learns 
them for his own farm only, and each must learn them for himself, or, at 
most, only over a limited area; while the geologist, studying them over 
wider areas, embracing hundreds or even thousands of farms, is enabled 
thereby to solve the questions of the individual more satisfactorily than 
he can do for himself, and to furnish him just that information which he 
needs in order that he may be able “ to make bigger potatoes and more 
in a hill.” 
Soils and Their Derivation. 
The unconsolidated and comparatively thin materials of the earth’s 
surface, which we know as Soil , and the subsoil which extends to various 
depths below it, have their origin in and depend for their character on 
the natural processes which have formed the earth and which are still in 
operation around us. Upon the seashore or the quiet lake, by the tiny 
rivulet or rolling river, in valley and plain, on mountain side or flaming 
volcano, in the action of the atmospheric forces, of the air itself, and of 
the snow and rain and frost and wind, we see the action of the natural 
powers which have fashioned the world as we find it, and which are ever 
busy corroding, decaying, and breaking down the solid materials, trans¬ 
porting the debris elsewhere and building it up anew, perhaps only to be 
remodelled in its turn. 
Over the greater portion of the surface of the earth these processes 
have taken hold of the existing rock materials, whether of sand or clay, 
of limestone or granite, or even of peat, and by the chemical reactions 
induced, and the assistance of the growth and decay of plants and ani- 
