GEOLOGY. 257 



Rock River, which stream enters the coal-field about 23 

 miles above its mouth, and has several good seams exposed 

 in the banks. 



" The coal in this vicinity is sure to become valuable, and 

 to be in great demand, for the reduction of such ores (espe- 

 cially copper ores) as are raised in those portions of the dis- 

 trict which are deficient in timber. Some town in this neigh- 

 borhood, or a little south, is destined to become the Swansea 

 of Wisconsin, and to receive, in its numerous furnaces, the 

 rich produce of the prairie mines, from the north and north- 

 west. 



" SALINES. 



" Throughout the Western States, generally, no produc- 

 tive salines are found below the true coal-measures. They 

 commonly occur in some of the lower members of the coal 

 formation, especially in the Avhite sandstones lying within 

 that formation, and at no great distance from its margin. 

 Such are the well-known saliferous rocks on the Kenhawa 

 and Muskingum. 



" As soon, therefore, as the character and extent of the 

 geological formations in the district were ascertained, I 

 ceased to expect the discovery of any productive salines, 

 except, perhaps, in the extreme southern corner of the tract, 

 where the great coal-field of Illinois stretches its lowest mem- 

 bers over a few townships. 



*' Every surface-indication confirmed my expectations. 

 No salt-springs, not a single salt-lick, no variegated shales, 

 not one of the usual indications of salt, were discovered. 

 Even in the southern townships, within the coal-formation, 

 the thickness of the strata is so inconsiderable that the chance 

 is very slender of reaching profitable brine. Salt, therefore, 

 cannot be reckoned among the productive minerals of Iowa 



