SO LIMESTONES OF RED CEDAR, 
REGION OF DRIFT RESTING ON LIMESTONES OF DEVONIAN DATE, 
SECTION III. 
ITS MINERAL CONTENTS. 
Tue structure and composition of the rocks which form the basis of this tract of 
country are not unfavourable for the retention of minerals; its physical features, 
however, do not indicate a mineral tract. Along the course of our route, no symptoms 
were observed of important axes of dislocation and disturbance. The surface is 
comparatively level; the ledges of rocks lie low and horizontal, without any abrupt 
uplifts or sudden faults, as if beyond the sphere of active action that has fissured, 
and filled with metallic matter, the magnesian limestones lying to the northeast, 
nearer to the Mississippi. 
SECTION IV. 
ITS RANGE, EXTENT, AND BEARINGS. 
Tue superficial area of the formation under consideration is much less than that 
of any other system of sedimentary rocks of the District. It may be traced along 
the course of the Mississippi River, for the distance of about thirty miles, viz. : from 
near the head of Rock River Rapids, a few miles below Parkhurst, to the town of 
Wyoming. Thence the formation ranges, with a northwesterly curve, up the valley 
of Red Cedar River ; forming a belt, averaging, at first, some twelve or fifteen miles 
only in width, but gradually enlarging, until, when in latitude 43°, it disappears 
— the drift of Northern Iowa, it attains a width of from thirty to thirty-five 
miles. 
Over a large portion of this tract of country, and especially on the high grounds. 
