Calvin on the (Deep Well at Waskingion, Icisoa. 29. 
earlier drift, and 350 feet of superficial detritus scarcely suffice 
to bring the surface up to the level of the limestone at the 
quarries west of the city 
At a depth of 45S feet the samples show a light colored 
magnesian limestone of rather fine texture. The borings from 
this depth contain the only recognizable fossils found below 
the "forest bed." Fragments of Atrypa reticularis Lin. and 
of Athyris vittata Hall, indicate very clearly the horizon of 
the Hamilton limestone and shales as these are developed at 
Iowa City, Davenport, or Independence, Iowa. 
With some alternations of shale and limestone the Devonian 
deposits extend to a depth of 500 feet. At this depth the last 
of the borings referable to the Devonian were obtained. 
The next samples are marked 532 feet and consist of calcif- 
erous sandstone, which at 5S5 feet passes into a purer sand- 
stone and as such is continued to a depth of 632 feet. As, 
however, the next sample is marked 702 feet, we may infer 
that the sandstone extends almost to that depth. This 170 feet 
of sandstone evidentlv represents the deposits of the Niagara 
period. 
At 702 feet we find a fine bluish or greenish shale, identical 
in all respects with shales of the Hudson River group, as seen 
in the bluffs at and belo^v Bellevue, lov^^a. • Clay shales, some- 
times with an admixture of sand, and again with some calcare- 
ous matter, are continued down to a depth of 793 feet. This 
group of shales are plainly referable to the Hudson River 
shales of Hall or the Maquoketa shales of White. 
Grayish limestones, not dolomytes however, from 803 to 963 
feet are probably the equivalents of the Galena limestone of 
eastern Iowa. 
At 1020 feet the borings consist of dark, fine-grained lime- 
stone mixed with considerable carbonaceous shale. There is 
little difficulty in recognizing in this limestone and shale the 
Trenton of Iowa and Wisconsin. The bits of carbonaceous 
shale are quite rich in bituminous matter and burn with flame 
and smoke when ignited. Similar shales, that one may light 
with a match, constitute partings between the beds of Trenton 
limestone at Boat-Yard Hollow, opposite Dubuque, at the 
mouth of the Turkev river, and at many other places in Iowa. 
