Association of American Geologists and Naturalists. 155 
neously supposed that volcanoes existed on the Upper Missouri. This, 
however, is a mistake. ‘The smoke and pseudo-pumice, he supposed 
to proceed from the same source, the ignition of the iron pyrites and 
lignite, which are found in great abundance in the plastic clay. These 
pseudo-volcanoes were not in action during the journey of Lewis and 
Clark, nor during that of Mr. N.; but every thing concurs to prove 
their existence ; the unanimous declarations of the Indians and voya- 
geurs—the blackened and sterile appearance of the more recent, and 
the name given to the district, cote brule, or “‘ burnt coast.”? The In- 
dians call these spots mankah zita, or ‘‘ smoking earth”—thus recoeg- 
nizing their difference from volcanoes, which would be called burning 
mountains. 
Mr. N. exhibited in illustration of his paper, his splendid map of the 
hydrographical basin of the Upper Mississippi, embracing an area of 
10° of latitude and of longitude, prepared for government and engraved 
on its order. This map is not yet published; but will soon appear in 
connection with the report of Mr. Nicollet, accompanied by a map of 
the same territory, on a reduced scale, with the topography exhibited 
thereon, as directed by a recent order of the Senate. Some notion of 
the extent of the territory embraced may be formed from the statement, 
that it is nearly once and a half as large as that of France. 
Mr. N. stated, for the benefit of future collectors, that the fossils and 
selenites, &c. could be obtained immediately after rains without the 
labor of digging, and that if favored with a brilliant sun they occa- 
sioned a beautiful appearance by their glittering lustre. Hence the 
name of “ shining hills,” so appropriately given by the Indians, and by 
them mentioned to the first white explorers. ‘This name had been sup- 
posed [erroneously] to apply to the Rocky Mountains. 
Prof. Rogers enquired of Mr. Nicollet, if there was any evi- 
dence of the existence of a saliferous formation south of the Yel- 
lowstone River. 
Mr. Nicollet replied, that he had no definite knowledge on the 
subject, having never been there. 
Dr. Houghton, referring to the rocks about the great Salt 
Lake, stated that these formations belonged to the strata of the 
lower portion of the coal series. 
Prof. Rogers said, that in confirmation of the remarks of Mr. 
Nicollet, as to the pseudo-volcanoes of the Upper Missouri, he 
would state that he had been informed by fur-traders and others, 
in whose statements implicit reliance could be placed, that high 
up on the Missouri and Yellowstone, there were these hills of 
burning clay, and that after they were burnt out they sunk down, 
