11G 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 3, 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 I 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 " tiff," 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-calcareous deposits, possessing a tuten- 

 mergel structure, and associated with Septaria, and isolated masses having the com- 



