12 NOTES ON THE NORTHWEST. 



these hills ; and, in truth, upon a distance 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 * les cotes hruUes ' — ' collines hruVees^ — 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 subteiTanean fires ; the 

 blacker and more sterile parts being the most recently burnt. 

 They are pointed out by the voyageurs, and I have indicated 

 several on my map. The fossil shells, that I have preced- 

 ingly enumerated, lose their brilliant opalescent appearance, 

 and are partly calcined, though still preserving their specific 

 distinctions. Layers of the clay are also met with, so 

 altered as almost to deserve the mineralogical name of por- 

 cellanite ; in fact, all the minerals belonging to the formation 

 exhibit the alteration which might be supposed produced by 

 exposure to that sort of action now to be assigned. 



" I believe that these pseudo-volcanic phenomena may be 

 compared with those described as occurring in other portions 

 of the globe, under the name of terrains ardens ; although 

 they are not here accompanied by the emxission of flames. 

 They are evidently due to the decomposition, by the perco- 

 lation 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 spontaneous combustion ; whilst further reac- 

 tions (well understood by the chemist) upon the Hme con- 

 tained in the clay bed, produce the masses and crystals of 

 selenite that are observed in the lower portion of this inter- 

 esting deposit. This is the theory which, with some Httle 

 confidence, we have formed of these pseudo-volcanoes. 



" It may be interesting to future travellers to learn that, 



