116 CARBONIFEROUS LIMESTONES 
ing Stigmaria. Thin beds of coal show themselves at several other places on Ros- 
seau’s Run, as well as at the following localities in this neighbourhood. A bed of 
inferior quality, two and a half feet thick, occurs on Section 4, Township 74 north, 
Range 18 west; another, two to three feet thick, on Section 6, Township 74 north, 
Range 17 west; and on White Breast River is a three-foot bed of pretty good qua- 
lity, on Section 38, Township 75 north, Range 20 west, three to five feet above the 
water-level. 
On Section 15, Township 74 north, Range 18 west, on Cedar Creek, a laminated 
sandstone, containing Lepidodendron Sternbergii, is seen extending ten or twelve 
feet above the water-level, overlaid by argillaceous shale. The latter contains 
many crystals of selenite, some of which are regular rhomboidal prisms, with the 
edges bevelled. Immediately under the range of selenite, the tutenmergel structure 
is apparent in the argillaceous beds. The same members present themselves on 
Honey Creek, on Section 35, Township 75 north, Range 18 west. This is the 
locality where diggings were undertaken in search of lead ore, but without any 
success, so far as | am able to judge, both from personal inspection and the most 
reliable information. The attraction on Honey Creek was doubtless the brilliant, 
yellow, metallic lustre of iron pyrites, disseminated in the dark, argillaceous shales, 
in connexion with the transparent crystals of selenite, which, under the general 
appellation of “ tif,’ was taken to be a sure indication of the vicinity of rich veins 
of galena. Nothing could be more unfavourable to the presence of profitable veins 
of that ore, than the schistose crumbling beds of argillaceous shale that crop out 
everywhere in the vicinity. A far more likely source of sulphuret of lead would 
be the underlying hard limestones, which, however, do not reach the surface in this 
vicinity. Yet even they are not likely to prove metalliferous in this district of 
Iowa, for reasons heretofore stated, and because there are no symptoms of outbursts 
of igneous rocks throughout this region, either in the shape of basaltic dykes, toad-' 
stone, or whinsills, such as traverse the mining districts of the carboniferous lime- 
stone of other countries. On the contrary, the landscape presents those gentle 
swells, dotted with groves and intersected with belts of timber, that form so cha- 
racteristic a feature of the rich farming lands bordering the valley of the Des 
Moines ; their wavy outline is seldom interrupted, except in the immediate vicinity 
of a water-course, by the protrusion of even a solitary ledge of rock, that might fur- 
nish a few slabs to wall a cellar or underpin a building. 
After examining this section of country, and endeavouring to trace the reported 
discoveries to their origin, I became pretty well satisfied that the small quantities 
of lead ore which have been found, either at the designated locality on Honey 
Creek or elsewhere in the vicinity, consisted of a few pieces, brought most probably 
into the country by Dubuque miners, and placed in the earth as a trick, or for the 
purpose of deception, in order to obtain money under false pretences. 
The geological formation of the Des Moines River, and its branches in the south- 
eastern part of Marion’ County, corresponds in many of its features with that of the 
northern part of Davis County. The selenite, at both localities, occupies the same 
relative position, just above the dark argillo-caleareous deposits, possessing a tulen- 
mergel structure, and associated with Septaria, and isolated masses having the com- 
