28 Soils of Nebraska — IlicJiS. 
buried deep under many feet of clays, sands, and gravels, so that 
their relation to the soil seems to be extremely remote. But 
these clays, sands, and gravels, which constitute the subsoil, are 
derived from the bed rocks, either those of the immediate 
vicinity, or the bed rocks of some region not very remote. All 
the mineral matter of soils and subsoils is derived from the bed 
rocks by decomposition and disintegration. I have already 
shown that the humus is dependent upon the mineral matter. 
Hence, the whole mass of the soil with all of its constituent 
elements is derived from the rocks. If all the loose material 
above the bed rocks were scraped ofE from the state of Nebraska, 
not many centuries would elapse until a new soil would be 
formed. If then we wish to understand the nature and origin 
of our soils, we must study the bed rocks. To facilitate this in- 
vestigation I present herewith a Preliminary Geological Map of 
Nebraska upon which the geological distribution of the bed 
rocks is represented. This map has cost me much labor in the 
field, but I do not claim for it anything more than approximate 
accuracy. It is such a map as a geologist would construct to 
illustrate a preliminary reconnoissance, not such as would ac- 
company the final report of a geological survey. 
By reference to this map you will see that the oldest forma- 
tion in the state is in the southeast. Underlying the counties 
of Richardson, Pawnee, Johnson, Nehama, Otoe, and Cass, and 
parts of Lancaster, Sarpy, and Douglas, the bed rocks are lime- 
stones, shales, and sandstones, with a few thin seams of coal. 
These rocks belong to the series of the Coal Measures of the 
Carbonic system. The coal in them is too thin and poor in 
quality to be of much commercial importance; still it is mined 
for local use in several counties. About 1,300 tons were taken 
out in 1887. Of the three kinds of rocks in the Coal Measures 
the sandstone is least important, both as to quantity, value as a 
building stone, and effect upon the soil. A few thick layers of 
it occur along the Missouri river, but it plays no important part 
in the industries or wealth of the counties underlaid by the 
Coal Measures. The shales are more abundant than either the 
limestones or the sandstones, constituting more than half of the 
entire thickness of the Coal Measures. They are of no value ex- 
ccept as the basis of soils and of brick and fire clays. The clays 
produced by the decomposition of shales are often of superior 
