1 30 Correspondence. 
the south. The larger part of the body of ore underlies a rounded hill 
or spur of the divide Ijing between two ravines tributary to the Village 
creek. The top of this hill at its highest point is slightly higher than 
the general level of the divide. As far as can be ascertained, the deposit 
has an area of about 300 acres and an average depth of thirty feet. The 
ore is a mass of concretionary brown hematite boulders, packed so closely 
as to form an almost solid ledge, the interstices and ca\ities being filled 
with a red ferruginous clay. 
This ore lies upon the undisturbed blue limestone which forms the 
lowest and oldest deposit of the Trenton epoch. I say undisturbed, for 
Avherever a shaft has been sunk through the or6 to the underlying lime- 
stone, it has invariably been found in its normal position of an almost 
dead level. I might remark here, that, although I have traveled over 
every part of this country, I have hever seen any fault or tilting of strata 
or any other indication in any of the formations exposed of an upheaval 
or disturbance of any kind. 
As the Trenton limestone thins out and disaj^pears (in Allamakee Co.,) 
on the upper part of the north slope of the divide between the Upper 
Iowa river and Village creek, it can not have a thickness under the ore 
bed of more than sixty feet. This limestone lies conformably upon the 
St. Peter sandstone, which outcrops on the tops of all the higher ridges 
in the north part of the county. It is worthy of notice that this sand- 
stone is everywhere, as exposed in this section, much colored by oxide 
of iron, and, in a few places, a thin layer of very good ore is found in the 
upper part of it. 
Immediately overlying the ore is a thin stratum of small drift gravel, 
such as is found in most parts of this county overlying the Trenton, then 
the usual yellow clay subsoil found in this section. This subsoil, the 
gravel, and the black surface soil are the only deposits overlying the iron. 
In no place do they exceed a thickness of ten feet, and should the deposit 
ever be worked this will make the operation of stripping very easy and 
cheap. 
Some of the upper boulders of ore are composed of very small drift 
gravel cemented together into a solid mass by the iron; others again are 
thickly encrusted with these small pebbles. On the occasion of one of 
my visits there, last fall, I picked up several pieces of ore in which were 
imbedded well-preserved specimens of Trenton fossils. 
A number of assays of the ore have been made and none of them 
showed less than fifty per cent, of iron, the highest being sixty-four per cent. 
Ellisox Orr. 
Postville, lov.-ci, Dec. ij, 1S87. 
A crystalline rock near the surface in Pawnee Co., Ncl>. During the 
past summer a rock of no little interest was brought to light in a boring 
by the Rock Island & Pacific railroad company in Pawnee Co., Neb. 
The surface formation is Carboniferous. For 532 feet there is an alter- 
