262 
ELDRIDGE. 
the coarse sediments of the lower division of the Trias—the 
Red Beds—which in time completely capped the hill along 
the line of profile given, and finally buried its summit deep 
beneath the accumulated material. General subsidence and 
sedimentation continued uninterruptedly to or nearly to the 
close of Triassic times, completing the first stage in the his¬ 
tory of events here considered. 
Second period .—At the close of the Trias the region which 
embraced the above events a second time yielded in a marked 
degree to the forces of elevation and developed the gentle 
arch of Triassic and Archaean strata shown in profile II. 
The north and south extent of this arch was but slightty 
greater than that of the one already described in Archaean 
times, its crown—coincident with that of the earlier one— 
lying about a half mile to the north of the present position 
of Clear creek. The rise of the arch, as indicated by its 
upper beds, was apparently about 420 feet, but subsequent 
erosion must have planed it down from its original height 
and shape to approximately the level line drawn across it 
in the figure as the base of the Jurassic formation. 
The evidence for the occurrence of the non-conformity at 
this horizon and the fold which preceded it is found in the 
disappearance of most of the upper members of the Trias 
within the region of its influence, and in the divergence be¬ 
tween the present strikes of the formations on either side of 
the line of unconformity—a divergence in strikes, it being 
remembered, corresponding to an equivalent discrepancy in 
the ancient dips, as shown in the profiles. 
This line of non-conformity is naturally somewhat wavy, 
and it is possible, indeed, that at some points along the mid¬ 
dle portion of the existing arch, through insufficient erosion, 
the deposition of a part or even of the whole of the Jura may 
not have taken place. The weight of the evidence, however, 
is in favor of nearly complete deposition over the entire sec¬ 
tion, from the fact that wherever the formation now exists 
it displays no tendency whatever to a protracted, gradual 
thinning, as is the case in the disappearance of certain of 
