STRUCTURAL FEATURES IN THE FOOT-HILL REGION. 261 
vation. The profiles, however, afford data quite sufficient to 
furnish a clear insight into the general character of the non¬ 
conformities and the movements in the earth’s crust which 
led up to them. 
Periods in the Development. 
First period .—Taking up now in detail the several events 
in the geological history of this region by which it has 
reached its present state of evolution, first: that which 
brought about the non-conformity between the Archaean 
and Trias. That there everywhere exists a general non¬ 
conformity between the rocks of these two ages is, of course, 
well known, but within the region in question there is direct 
evidence of a special development of the non-conformity, 
which is, furthermore, borne out by the subsequent e-vents 
which form the successive steps in the geological history of 
the area. This evidence consists in the observed termina¬ 
tion of certain of the lower beds of the Trias against a 
slightly projecting portion of the Archaean; in the impossi¬ 
bility on structural grounds of the whole amount of thin¬ 
ning which the Triassic beds have undergone being attribu¬ 
table to disappearance from the top and the consequent 
necessity for its having taken place from below ; and in the 
graphical development of an Archaean eminence, as repre¬ 
sented in profile I, by tracing backward from their present 
positions through the series of figures given, the relative move¬ 
ments of the rocks of the several ages by which they have 
been brought into these positions. The evidence is found 
to lead directly to the following conclusions regarding the 
first of the periods in the special history of this region with 
which we have to deal. 
Prior to the deposition of the Trias there had been de¬ 
veloped in the Archaean, partly by erosion and partly, per¬ 
haps, by compression, the elevation shown in section in pro¬ 
file I. Its height was probably 800 feet, and it had a linear 
extent in a north and south direction of nearly four miles. 
Against the sides of this Archaean elevation were laid down 
