I 237 ] 40 



cended the Missouri in 1839 ; and so would seem to have been the case at 

 the passage of Lewis and Clark at the beginnrng of this century. But, 

 previous to my arrival, since the memorable expedition last referred to, and 

 during a period of three years, they were seen (as my information goes) by 

 many intelligent persons engaged in the fur- trade, all of whom are natu- 

 rally observant, and most of them of unquestionable authority. 1 have no 

 doubt, therefore, of the existence of these hills; and, in truth, upon a dis- 

 tance of 130 miles from Scalp mountain to beyond the Karmichigah, or 

 Great Bend, there is nothing to be seen but a black zone, known to the 

 voyageurs as " /es coles brnlees''' — '■* colli nes brulees,-' — viz: burnt bluffs, or 

 burnt hills. 



In other respects, the character of the vegetation, which is always scant 

 upon this zone, indicates, in a measure, the epochs when it was visited by 

 these subterranean fires; the blacker and more steril parts being the most 

 recently burnt. Tliey are pointed out by the voyageurs, and 1 have indi- 

 cated several on my map. The fossil shells, that 1 have precedingly enu- 

 merated, lose their brilliant opalescent appearance, and are partly calcined, 

 though still preserving their specific distinctions. Layers of the clay are 

 also met wiih, so altered as almost to deserve the mineralogical name of 

 porcellanite ; in fact, all the minerals belonging to the formation exhibit the 

 alterations which might be supposed produced by exposure to that sort of 

 action now to be assigned. 



I believe, and it is also the opinion of my friend Professor Ducatel, to 

 whom I submitted my specimens, that these pseudo-volcanic phenomena 

 may be compared with those described as occurring in other portions of the 

 globe, under the name of ttrraiii.s aniens ; although they are not here ac- 

 companied by the emission of flames. They are evidently due to the de- 

 composition, by the percolation of atmospheric waters to them, of beds of 

 pyrites, which, reacting on the combustible materials, such as lignites and 

 other substances of a vegetable nature in their vicinity, give rise to a spon- 

 taneous combustion ; whilst further reactions (well understood by the chem- 

 ist) upon the lime contained in the clay bed, produce the masses and crys- 

 tals of selenite that are observed in the lower portion of this interesting de- 

 posits. This is the theory which, with some little confidence, we have 

 formed of these pseudo-volcanoes. 



It may be. interesting to future travellers to learn that, in order to collect 

 both fossils and most interesting specimens of crystallized selenite, without 

 taking the trouble of making diggings, it is only necessary to perambulate 

 the zone of plastic clay shortly after it has been washed by heavy rains. 

 Under such circumstances, should they be favored moreover by the reflec- 

 tions of the snn, they will be struck with the appropriateness of the desig- 

 nation of these hills, as applied both by the voyageurs and Indians — name- 

 ly, of shining monnlains. In truth, it is not unlikely that these hills, a 

 portion of ihera attaining an elevation of from 500 to 700 feet above the 

 river, were some of those referred to by the Sioux of the Mississippi, who, 

 conversing with the first white njen v/ho visited them, and long afterwards 

 with Captain Carver, spoke of the shining mountains of the west. 



These (so named) pseudo-volcanoes are not, however, confined to the 

 valley of ihe Missouri. Traces of them are not uufrequently found over 

 the more westerly regions, as flir as the upper portions of the rivers 

 called by the Indians Majikizitah and Washtey. The name of Manki- 



