AMERICAN GEOLOGISTS AND NATURALISTS. 33 



Mr. N., broken in health and his means exhausted, returned to Bal- 

 timore, where he soon received a flattering invitation from the war 

 department and topographical bureau to repair to Washington. The 

 result of his travels having been made known to these departments 

 and appreciated by them, he was intrusted with the command of 

 a new expedition, to enable him to complete to the greatest advan- 

 tage of the country, the scheme which he had himself projected in 

 his first visit to the far West ; namely, the construction of a map of 

 the region explored by him. Tliis map having been recently sub- 

 mitted to Congress, the senate of the United States has, unani- 

 mously, ordered its publication under the direction of the tojjograph- 

 ical bureau. It is to be accompanied by a report embracing an ac- 

 count of the physical geography of the country represented, together 

 with the most prominent features in the geology and mineral resour- 

 ces of other sections of our western states not embraced within the 

 limits of the map. 



Mr. N. then went on to give a succinct account of his geological 

 researches, which, modestly disclaiming any pretensions to be con- 

 sidered a professed geologist, he had felt an hresistible inclination to 

 engage in, as a subject of general and growaog interest. This ac- 

 count he offered as a more appropriate theme, in view of the ob- 

 jects contemplated by the present meeting. 



Mr. N. said he had traced a magnesian limestone — the clifi^ lime- 

 stone of Dr. Owen — which is probably referable to the mountain 

 limestone of European geologists, over a vast extent of country, 

 within the valley of the Mississippi. Connecting his own researches 

 with the facts brought to light in the survey of the Iowa and Wis- 

 consin Territories by Dr. D. D. Owen and Prof John Locke, and 

 with the observations of Dr. Henry King, during an exploration of 

 the country watered by the Osage river, Mr. N. thought himself 

 warranted in assigning the Falls of St. Anthony on the Mississippi 

 river, as the northern limit of this formation, which to the West, 

 extends to Fort Leavenworth on the Missouri river, and to the 

 South, embraces the metalliferous region of the state of JMissouri. 

 This limestone, containing Trilobites, Catenipora, and other coralline 

 fossils, is the metalliferous rock not only in Missouri, but in Iowa 

 and Wisconsin, from which the lead and copper ores are extracted. 

 The rock intervening between it and the coal formation is charac- 

 terized by the occurrence of the Pentamerus oblongus. In this rela- 

 tive position, also, are found thin beds of oolitic limestone, that are 

 perhaps referable, geologically, to the oolitic limestone of Tennes- 

 see, described by Dr. Troost, who indicates the Pentremites as their 

 characteristic fossil ; a large number of these fossils, in a loose state, 

 was collected in the vicinity of these rocks. Shallow coal basins 

 frequently occur in Missouri and the south part of Iowa Territory ; 

 but on the Mississippi river, the coal disappears, about thirty miles 

 above St. Louis ; thence, ascending the river as far as the great 

 Platte river, the cliff limestone and the coal rocks present them- 



