1874.] 257 [Allen. 



except that there were greater appearances of burnt hills, furnishing 

 large quantities of lava and pumice stone, of the last of which we ob- 

 served pieces floating down the river, as we had previously done as low 

 down as the Little Missouri." 1 These appearances continue to be 

 noted by these observers as far as the Yellowstone. At the mouth of 

 Martha's River, a little above the Yellowstone, they remark: " There 

 are greater appearances of coal than we have hitherto seen, the strata 

 of it being in some places six feet thick, and there are strata of burnt 

 earth, which are always on the same level with those of the coal." 2 

 A little below Porcupine River they speak of the hills as having " be- 

 come lower, and the strata of coal, burnt earth and pumice stone " 

 as having " in great measure ceased, there being in fact none to-day." 3 

 A little further on, at a point some thirty or forty miles below the 

 mouth of Milk River, they again refer to the entire cessation of these 

 appearances. 4 At Teapot Island, some distance above the Mussel- 

 shell, however, the appearance of coal and pumice stone is again no- 

 ticed. 5 About Elk Rapids, and thence nearly up to the mouth of the 

 Judith River, the continued " appearance of coal, burnt earth, pum- 

 ice stone, salts," 6 etc., is noted, beyond which is no mention of these 

 phenomena. It hence appears that these metamorphic phenomena 

 begin on the Missouri at a point some distance below Fort Berthold, 

 probably near Fort Clark, and extend thence, with occasional inter- 

 ruptions, nearly to the Judith River ; that near Fort Berthold, be- 

 tween the mouths of the Little Missouri and Yellowstone, and be- 

 tween the Yellowstone and Elk Prairie Creek, and also at a locality 

 some distance above the Musselshell, are districts where the metamor- 

 phism produced by the burning out of the lignite beds forms a strik- 

 tng feature in the topography of the country. Both above and below 

 the Musselshell for a considerable distance, owing to an extensive 

 outcrop of the cretaceous beds at this point, none of this metamor- 

 phism appears to have been observed. 



Dr. Hayden has reported the occurrence of one locality of this met- 

 amorphism west of the main chain of the Rocky Mountains, on the 



i Lewis and Clarke's Exped., Vol. i, p. 190. 



2 Ibid., p. 201. 



3 Ibid., p, 203. 

 * Ibid., p. 208. 

 e Ibid., p. 229. 

 « Ibid., p. 230. 



PROCEEDINGS B. S. N. H. — VOL. XVI. 17 MAY, 1874. 



