
. i. Pim 

CRETACEOUS AND TERTIARY—GENERAL ARRANGEMENT. 145 
commencing at its first appearance near Milk River, we find it covering 
an area of two hundred miles in length, and sixty in breadth; or, about 
twelve thousand square miles. I have been thus particular in estimating 
its approximate limits and extent of surface, on account of its influence 
on the future destiny of that region. Wherever this deposit prevails, 
it renders the country more completely sterile than any other geological 
formation I have seen in the North-west. We see from the above 
estimate that it renders barren, over thirty thousand square miles of the 
valley of the Missouri.” * The contrast between the country resting on 
this formation, and that based on the Lignite Tertiary, is very striking, 
and even in regions where the vegetation is stunted from the want of 
sufficient moisture, and where the dry uplands of the Tertiary would 
seem, at first sight, less favourable than the low-lying plains of No. 4; the 
former can support a short thick growth of nutritious grasses, where the 
latter has the character above described. In tracing the outlines of the 
various formations in a country where exposures are usually so rare and 
small, this difference of character in the aspect of its surface, is soon 
remarked as a valuable aid. 
353. These remarks, however, only apply in their entirety to the 
region south of the great transverse watershed, which approximately 
follows the forty-ninth parallel; and to the higher ground toward the base 
of the mountains. Wherever the causes which have produced the thick 
drift deposits of the plains, have operated in their full intensity, the influ- 
ence of the underlying beds on the soil, has been greatly modified by the 
addition of transported material. This modifying action has perhaps no- 
where been more effectual, than over the areas covered by No. 4, which, 
from its comparatively yielding character, has been cut away into hol- 
lows and buried under great depths of travelled material. The improve- 
ment thus effected on the country is especially notable between Pembina 
Escarpment, and the Missouri Coteau. I cannot speak from personal 
knowledge of the country south-west of the upper parts of the Red River 
Valley, but it is probable that the drift agencies have here, to a certain 
extent, over-ridden the low barrier of the water-shed. Further west, and 
south of the Tertiary plateaus of Wood Mountain, and the Cypress Hills, 
the barriers to the north-eastern drift appear to have been nearly com- 
plete. 
354. As already mentioned, the waters of springs flowing from all 
*Notes explanatory of a Map and Section of Country bordering on the Missouri. 1857. 
10 D 
