J. LeConte—Structure and Origin of Mountains. 105 
how a range haying the structure of the Appalachian, the Coast 
range, the Sierra, the Alps or the Caucasus, i. e., a range con- 
sisting of many closely appressed folds, could have been formed 
except by horizontal pressure. It is, I believe, equally zncon- 
ceivab-e that horizontal pressure on a large scale can be produced 
otherwise than by interior contraction of the earth. Ranges con- 
sisting of a single fold like the Uintah are equally well explained 
by the same kind of pressure ; and therefore it seems unneces- 
sary to seek a different explanation for these. My own con- 
viction therefore is that all mountain ranges have been formed 
in a substantially similar manner. But since the publication 
my papers, some objections have been urged against this 
conclusion, which must now be examined. 
by north and south cliffs of the Plateau region, and the parallel 
escarped, monoclinal ridges of the Basin region are more prob- 
ably produced by direct, upward lifting forces. But we have 
already shown that these are not monogenetic ranges at all, but 
only the displaced parts of one great monogenetic bulge. There 
has indeed been a vertically acting force concerned in forming 
these ridges ; but it was not a vertically up-lifting but a vertically 
down-pulling force. It was a mere gravitative adjustment of 
the broken parts of the great arch lifted as usual by horizontal 
pressure, 
solid earth. I have long felt this as a really serious objection 
to the special form of the contractional theory expressed in my 
