STRUCTURAL FEATURES IN THE FOOT-HILL REGION. 271 
and south of the field, accompanied by a variation from its 
normal western direction to directions diagonal to the range 
and divergent as this is approached, by which the original 
north and south compressive forces would have been com¬ 
pensated by the components of the later one acting in the 
reverse direction respectively (B, Fig. 2). Equilibrium hav¬ 
ing been restored over the area in question, and a portion 
of the affected region having become involved in the gen¬ 
eral uplift of the range, which still continued, by subsequent 
erosion and the formation of the plane surface of the present 
day the underlying strata became exposed in the superficial 
section now existing. 
7 th. Relation of the basalt eruption to the above events .—The 
eruption of the Table Mountain basalt took place e&rly 
in the period of the Denver formation, approximately after 
the deposition of about one-third of the series had been com¬ 
pleted and some time before the strata had assumed the ex¬ 
tremely high angles they now have. With regard to its re¬ 
lations to the phenomena forming the subject of this paper, 
it is possible that the subsidence of the Niobrara fold and 
the horizontal beds capping it may have been, in its later 
stages, synchronous with the eruption of the basalt masses 
in Denver times and perhaps in a measure due to it. The 
fissures through which the pent-up lavas found relief may 
have been the result of the almost constant bending to . 
which the rocks were subjected, and their appearance may 
have thus constituted the final event in the history of a 
place remarkable for its dynamic movements. 
The Views of Others on the Structure of this 
Region. 
Before closing this paper it is desirable to notice the views 
of the late Mr. Marvine and Professor Ward in regard to the 
structure of this region. 
The views of Marvine .—These are given in Vol. VII (1873) 
of the Hayden Reports, where he has expressed in the briefest 
possible manner the idea of non-appearance of strata due to 
30—Bull. Phil. Soc., Wash., Vol. 11. 
