262 The Aliierican (itohxj'lHt. October, 1891 
border. In the former occur nearly all the large and workable deposits. 
The ores of the Batesville region occur in a residual clay, derived 
from the decay of a limestone which, according to Prof. H. S. Williams, 
occupies a position intermediate between the Trenton and the Niagara 
limestones. The ores of the southwestern part of the state are in 
novaculite probably of Lower Silurian age, perhaps Trenton. The ores 
in both regions are in the forms of the various oxides of the metal. 
These ores were mentioned by Owen and Cox, and Featherstonhough 
mentioned manganese in the southeastern part of the state, but it is 
only within a few years that there have been systematic working and 
descriptions of the deposits. 
Between the ore-bearing St. Clair limestone, which is of about the age 
of the Trenton, and the Boone chert which is a part of the lower Car- 
boniferous, is a curious clayey deposit which is partly the result of sur- 
face decay of the lower limestone, and partly apparently of the nature of 
eruptive ash. This has been but partially investigated, but it seems to 
be widespread, and points to a long land exposure in this region between 
the close of the Lower Silurian and the age of the Carboniferous Boone 
chert. This had already been suggested by Dr. Branner from examina- 
tions in the field. Like the Cincinnati anticlinal, therefore, this part of 
the country experienced an elevation, but not like that, this remained 
dry land through the upper Silurian and the Devonian, and was subse- 
quently again sunk beneath the ocean. 
In the careful description of the manner of occurence of the ore in 
the Batesville region is ample proof of the thoroughness and ability with 
which the investigation has been carried on. It is a comparatively new 
'field, and it has been most satisfactorily worked. The ore occurs in a 
clay which is the residuum of the St. Clair limestone. The ore was first 
in the limestone. The decay of the rock, and the removal of the soluble 
part has concentrated the insoluble, this embracing the ores — which, 
however, have to some extent been converted from carbonates. This 
process of decay began after the last elevation of the region above the 
ocean and is still going on. This residual clay has nothing to do with 
the layer of residuum which naturally intervenes between the St. Clair 
limestone and the Boone chert already mentioned, as to its age and 
stratigraphic relations, however closely they may be related genetic- 
ally. 
The report embraces a review of the manganese mines of the United 
States, with a view to comparison with those of Arkansas, for the pur- 
pose, evidently, of arriving at some conclusion as to the origin of the ore 
in the rock from which it is now plainly derived by natural concentra- 
tion in iiitu through slow decay. In the course of this review, Dr. 
Penrose describes, with more fullness and correctness than has ever been 
done before, the manner of the occurrence of the iron and manganese 
ores of Vermont, and their stratigraphic relations. In this he adopts 
the late conclusions of United States geological survey (by J. E. Wolff), 
that the associated rocks are of the age of the Lower Cambrian, or 
Taconic of the region, as has been claimed from the time of Emmons 
