LACCOLITHIC MOUNTAINS 
27 
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Cretacic strata, and the bowing of the sedimentaries over the 
dome formed by the bulging body. In his investigation of the 
Sierra El Late in the following year Holmes^ presented the essen¬ 
tial features of laccoliths almost as clearly as did Gilbert those of 
the Henry Mountains several years later. Peale® further recog¬ 
nized the laccolithic peculiarities of the Sierra La Sal, and especi¬ 
ally emphasized the idiosyncracies of formation.® 
In this connection no special reference is made to the observa¬ 
tions of others who describe isolated mountains with eruptive 
nuclei surrounded by tilted sedimentaries having quaquaversal 
dips, but who give no intimation of the real structures. Among 
these, however should be noted the records of F. V. Hayden, in 
the Geology of Yellowstone Park Expedition, Henry Newton, in 
the Geology of the Black Hills, G. M. Dawson, in the Geology of 
the Forthy-ninth Parallel, and N. H. Winchell, in the Geology 
of Ludlow's Reconnoissance of the Black Hills. 
When, then, the Geology of the Henry Mountains was published 
in 1879, without recognition of any previous work along the same 
lines about all that there was left that was really new was to fix 
the type by giving it a specific name. Because of this fact, and 
Gilbert’s monographic treatment of a single phenomenon there¬ 
by drawing upon him the chief criticism of the hypothesis of 
origin his predecessors in the field were lost sight of. In view of 
later developments the tectonics of the Henry Mountains have to 
be examined anew with normal orogenic conditions in mind. 
The basis of the accompanying notes is a collateral result of 
some recent mine inspections. Chance diverted the inquiry from 
the questions of ore deposition after the latter had been disposed 
of to the broader geologic problem of association of the laccolithic 
intrusions with the tectonic features. Later other laccolithic fields 
were visited. Opportunity did not present itself to review the 
Henry Mountains on the ground and in the light of the recent 
tectonic results; but enough is gathered from the published ac¬ 
counts and from inspection of other southern Utah laccoliths to 
indicate clearly that some of the more notable of the ascribed fea¬ 
tures must be interpreted anew. 
7 Ibid., Ninth Ann. Rept., for 1875, p. 268, 1896. 
8 Ibid., Ninth Ann. Rept., for 1875, p. 95, 1876. 
9/Hcf., Bull. No. 3, p. 557, 1877. 
