STRUCTURAL FEATURES IN THE FOOT-HILL REGION. 273 
on the east side of the Cretaceous, with its upper strata at the 
extreme eastern, while the coal seam at its base occupied the 
extreme western side of the displaced rock. The degree of 
inversion varies slightly at different points, and may have 
been much greater in some places. This will probably ac¬ 
count for the discovery at one time of a certain Cretaceous 
shell (Mactra) above a vein of coal in a shaft about four miles 
north of Golden, and about which considerable has been said 
in discussing the age of the Laramie group. I visited the 
spot, but found the strata so covered by wash that I was 
unable to determine their nature.” 
In the above views there are four points demanding re¬ 
plies, although one—that regarding a certain Cretaceous 
shell—is somewhat irrelevant. The first point is the re¬ 
mark as to the conformability of all the strata from the 
Denver beds to the Montana group. Although no discrep¬ 
ancy in dip or strike is noticed between them in the vicinity 
of the Table Mountains, a study of the whole region has 
abundantly proved the existence of several non-conformities, 
by evidences of erosion, by the areal distribution of the out¬ 
crops, and by the character of the component materials of 
the various formations. The second point is the crevice near 
the western base of Table Mountain through which issued 
the basalt of the region. As a matter of fact, no evidence of 
such a crevice, nor of the dike which would still remain as 
its filling, exists along the well-exposed base of the hills. 
Furthermore, the outpouring of the basaltic sheets is entirely 
accounted for by the great Ralston dike and the irregular 
eruptive body near its southern end, and hence there is no 
necessity for assuming a further fracturing of the strata to 
give it a vent at some other point in the field. The third point, 
the fault, into which Professor Ward has developed the break, 
beyond a doubt coincides in locality with the great fold which 
occurs all along the eastern base of the Colorado Range, by 
which the beds to the west of it are sharply upturned, often 
to a vertical or reversed dip, while their continuance to the 
east of the axis is at a dip of but the slightest amount. This 
