OF THE UPPER MISSOURI. 99 
is nowhere better exhibited than in the country bordering upon the Yellowstone. Often 
ranges of hills extending back from the river into the interior for several miles, form a 
series of high bluff ledges of the fused or semifused rocks, somewhat variegated, but 
mostly of a lively red color, giving to the country the appearance of the ruins of a large 
city. The light vesicular pumice-like masses have been scattered by the wind over the 
plateaus surrounding these hills, and are sometimes carried a mile or more from the ori- 
ginal position. Even at the present time, I observed several places where the lignite beds 
were in a state of combustion, both on the Missouri and on the Yellowstone, and the 
atmosphere is filled with smoke, and the sulphurous smell which issues from these fires is 
exceedingly offensive to the traveller, 
The same phenomena have been observed in the far North, in the lignite beds on Mac- 
kenzie’s river, Mr. Simpson, a gentleman who travelled quite extensively in the Hud- 
son Bay territory, from 1836 to 1839, says of the beds of that region,—* Wood-coal was 
in a state of combustion for several miles on both sides of the Mackenzie, and these 
natural fires seem to have spread considerably since last described by Dr. Richardson. 
The jets of smoke issuing in many places from the perpendicular face of the clayey cliffs, 
presented a singular spectacle. The combustion had in many places scorched the layers 
of unctuous earth that interstratify the coal formation, and turned their surface to a 
lively red color,”* 
In regard to the age of the lignite formations described by Mr. Simpson, we have no 
reliable information, It is probable that they are synchronous with those on the Upper 
Missouri, but some portion of them may belong to the Cretaceous period. 
We will now return to the Missouri river, and trace the lignite strata westward, into 
the interior toward the Black hills along their southern boundaries. In latitude 463°, 
longitude 1002°, near the mouth of Cannon-ball river, we have distinct indications of this 
formation in the numerous conical hills which have been left after denudation; and 
scattered around these denuded hills are many fragments of finely preserved silicified wood, 
with a few estuary shells. Proceeding in a southwest direction from the mouth of Can- 
non-ball river, we find the outliers of the lignite formation, resting upon Cretaceous bed 
No. 5 of the vertical section, and on reaching Grand river, eighty miles above its mouth, 
the Tertiary strata occupy the surface of the country, the Cretaceous beds appearing only 
in the channels of the streams. At Thunder Butte we have a fine section of the Tertiary 
beds. This is a hill left after the denudation of the surrounding country, rising above the 
level prairie to the height of three hundred feet. The strata are perfectly horizontal, and 
the following beds in descending order will show the character of the hill: 
* Thomas Simpson’s Journal of Discoveries on the North Coast of America, during the years 1836 to 1839 ; 
pages 97 and 98. 
