20 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
sands and gravels, as has been suggested, but rather to the recent dis- 
placements of the mountain mass, as Gilbert has explained them.  ' 
Not far northeast of Payson canyon there are low rock-like mounds 
in the piedmont slope, as if here a part of the down-faulted mountain 
mass were still to be seen; but they lay too far aside from our road 
to be examined. 
Between Payson and Santaquin, in the neighborhood of the village 
of Pondtown, the mountain base is below Bonneville level, and here 
several rather well defined spur terminals 
have the Bonneville shore line slightly 
marked across the middle of their tri- 
angular facets, as in figure 3. In such 
a case it is evident enough that the facets 
cannot be the work of lake waves; and 
Fig. 3. A tacetted spur crossed... thus such. an origin is made unlikely in 
by the Bonneville shore line, 
near Pondtown. other places as well. 
. Between Pondtown and Santaquin, 
the gently convex base line of the range is clearly discordant with the 
mountain structure. About the middle of the base line a series of 
lighter colored strata dip into the mountain below the darker strata 
that form the higher slope; but towards either end of the base line 
the darker strata gradually descend to the base line, and the lighter 
colored strata disappear underground. Such discordance of form 
and structure, coupled with the simple curvature of the base line, 
the sharp cut ravines on the mountain face and the somewhat facetted 
spur-ends between them, must be taken as strong witnesses for the 
fault-block origin of the range. Next south of Santaquin, there are 
several outlying rock masses, west of the general mountain front, 
but their relation to the mountain was not clearly made out. 
The Wasatch Front from Santaquin to Nephi. This southward 
stretch of 20 miles gave the most unequivocal evidence of block fault- 
ing and elaborate carving, particularly well displayed near the little 
village of Mona. - To the north, as far as Spanish fork, the attitude 
of the strata is as a rule not particularly well exhibited, presumably 
because there are no contrasts of hardness or color of sufficient strength, 
whereby the relation of structure and form should be brought out: 
but south of Santaquin the resistance of successive members of the 
stratified series in the mountain face becomes more varied, and 
structure is displayed in form with satisfactory clearness. The strike 
of the strata is seen to be northeast-southwest, with strong and vari- 
able dips to the southeast. As a result, the ridges and valleys that 
