6 
Bulletin 65. 
soil material is of different origin is the occurrence, now and then, 
of a fragment of an impure limestone, which lies just out side the 
first hogback and belongs to the Fort Benton group or of sandstone 
belonging to the Juratrias. These fragments are quite rare and 
are the only definite proof that I have discovered that any portion 
of the soil has been derived from any other source than the granitic 
area of the mountains proper. The abundance of mica and red 
orthoclase in the coarser portions of the soil, and even in the silt, 
leaves no doubt but that this is the source of the material. 
Some of the material may be the residue of strata belonging to 
formations of later or post cretaceous times, whose removal by 
waters, now represented by the Poudre river, has left some of this 
material. This is undoubtedly true of much of the plains soil, but 
probably only to a very limited extent of the soils of these old 
water courses. 
SOURCE OF THE ALKALIES. 
§ 9. The alkalies are not so easily traced. The explanation 
offered for the presence of alkalies in the soils of arid regions is as 
true here as elsewhere, but these general facts are not applicable in 
the explanation of the particular cases with which we meet in Colo¬ 
rado agriculture. It is a well known fact, one long since recognized, 
that the shales of several of the cretaceous groups contain a remark¬ 
able amount of these salts, designated by the general term alkali, 
including sodium, calcium, and magnesium as sulfates, carbonates, 
and chlorids. 
GENERAL COMPOSITION OF THE ALKALIES. 
§ 10. Analyses of incriistations from various parts of the State, 
and of waters from both ordinary and artesian wells, show the very 
general distribution of these salts. They also corroborate the obser¬ 
vation of their presence in the shales and other rocks which, what¬ 
ever may have been the origin of the salts, serve at the present 
time to furnish the alkalies to the waters percolating through them. 
The following figures, representing the general composition of the 
alkali, will serve to illustrate the general application of the asser¬ 
tion. An incrustation from the College Farm showed: 
Calcic sulfate_25.451 percent. 
Magnesic sulfate_19.798 per cent. 
Sodic sulfate_41.748 per cent. 
The ground water from about five feet below the surface yielded 
an abundant residue, composed of: 
Calcic sulfate-35.648 percent. 
Magnesic sulfate_28.750 per cent. 
Sodic sulfate_11.393 percent. 
