■i- The American Geologist. Jan. 1891 
closed pebbles ace clearly of a foreign character. I have examined 
the ground all the way from the place of deposition to the head 
of the rivers and T find no trace of these rocks in situ. This is 
upon the Middle Loup. Upon the North Loup there is more 
gravel than upon the Middle. Eight miles north of Ord at the 
mouth of Gravel creek there is a heavy deposit of gravel and 
Band. This deposit is quite extensive and has a maximum thick- 
ness of 20 to 25 feet. Chert and silicified wood are very abun- 
dant. At Almeria upon the North Loup there is an important 
gravel deposit. Its extent and thickness are less than the one 
previously mentioned. In all these gravels of Valley and Sher- 
man counties, there is a resemblance. The mineral species are 
nearly the same. 
Two questions at once arise. Are these gravels and clays 
synchronous ? What is the age of the deposits ? As yet I see no 
clear answer. It is a favorable circumstance that these beds are 
quite general in extent. Undoubtedly some place will be found 
where a correlation can be made. As to the age the conviction is 
firm in the writer's mind that future investigation will enable 
1 hem to be checked with horizons of known age. These are the 
lines that future study must follow. 
Passing from Sherman into Greelv county another unconformity 
is observed. The strata here are not the clays, gravels, and Loess- 
like material as in the preceding instance. They are on the con- 
trary strata of unquestioned Tertiary age and the Loess-like forma- 
tion. This particular unconformity is well worthy a careful 
stud}'. Upon the western bank of the North Loup river and 
near the town of Scotia there is an outcrop of white, chalky lime- 
stone. In places this limestone is almost pure calcium-carbonate. 
Again it contains impurities, as silica and magnesia ; the mag- 
nesian ingredient manifesting itself as dolomite. Chert indicates 
the presence of silica. The entire outcrop has a thickness of 
some 80 feet. The eastern face of the scarp is washed by the 
North Loup river. Above and back the limestone is covered by 
the Loess-like formation. 
The fossils from the' chalk-bluffs are not abundant. However, 
Planorbi$, Physa, Limnoea and Vtviparus were generically 
determined. Aside from these several small Lamillibranchs were 
found, but their identification was impossible. The Planorbis 
occurs in such numbers as to render inanv of the broken faces of 
