Origin of Mountains. 429 
”? 
dependent on plication and crushing beneath, so complete a 
disappearance afterward would have been very improbable. 
Such facts as the above appear to prove that elevatory move- 
ments have often been, like those of subsidence, among the direct 
results of lateral pressure. The facts are so well known and 
the demonstration so generally accepted as complete, that I 
have suspected that there is here an unintentional omission or 
oversight in Prof: LeConte’s paper. 
3. Kinds and Structure of Mountains, 
result of one process of making, like an individual in any process 
of evolution, and which may be distinguished as a monogenetic 
range, being one tn genesis ; an 
composite or polygenetic range or chain, made up of two 
or more monogenetic ranges combined 
The Appalachian chain—the mountain region along the 
Atlantic border of North America—is a polygenetie chain ; it 
consists, like the Rocky and other mountain chains, of several 
monogenetic ranges, the more important of which are: 1. The 
Highland range (including the Blue Ridge or parts of it, and 
the Adirondacks also, if these belong to en eee rocess 0 
at 
making) pre-Silurian in formation; 2. The Green Mountain 
: 2 uring its 
closing period ; 3. The Alleghany range, extending from south- 
