22 On the Pumice of the Missouri. 



light, red, and porous masses, like those found floating on the 

 Missouri, to the compact and dark-coloured greenstone, which 

 is the prevailing rock in that formation. 



It was suggested by Mr. Bradbury, and the opinion has 

 been very generally adopted, that the origin of the supposed 

 Pumice of the Missouri is to be ascribed to the agency of ex- 

 tensive subterranean fires., believed to exist in the coal-beds 

 about the upper branches of that river; but it is well known 

 that the long continued burning of many coal mines in places 

 open to frequent examination, has not been found to give ori- 

 gin to substances of this sort. The obstinacy with which the 

 mineral, in its present form, withstands the operation of heat, 

 seems also to afford an argument unfavourable to this opi- 

 nion. 



Reports are frequent among hunters and travellers, who 

 have visited the country about the Falls of the Missouri, the 

 Yellow Stone, and the Eastern Ranges of the Rocky Moun- 

 tains north of the Platte, which have been thought to justify 

 the opinion that subterranean fires are now in existence in 

 that quarter. We are told of natural chimneys, lined with 

 soot, and which are sometimes seen to smoke, rising out of 

 the summits of hills, about which are found large quantities of 

 slag and cinder, like those of a blacksmith's furnace; and of 

 other appearances confidently supposed to indicate the ex- 

 istence and the present activity of volcanic or pseudo-volcanic 

 fires. Some have gone so far as to give a circumstantial de- 

 scription of a deep and wide chasm in the side of a mountain, 

 called Coulters Hill, out of which flames and smoke have of- 

 ten been seen to issue. 



Those who have had frequent occasion to trace to their 

 origin, popular traditions and the highly fanciful hypotheses 

 of men little accustomed to the attentive examination of ordi- 

 nary phenomena, will readily believe that the accounts above 

 mentioned, may have had no other foundation than the occa- 

 sional discovery about the upper branches of the Missouri, of 

 some varieties of Amygdaloid, or some other black and porous 



