INTRODUCTION. 
83 
limestones of that age, constitute a large part of the mass producing 
the altitude of that range of mountains* *. 
If it be true that original deposition or accumulation has given origin 
to mountain ranges, then, the greater that accumulation, the higher 
will be the mountain chain ; and if, after the formation of the older 
strata along certain lines, there shall supervene conditions allowing the 
deposition of later formations above the older ones, we may, on the 
final elevation of the continent, have mountains of greater altitude 
composed of strata of successive ages. I can conceive, moreover, that 
under analogous circumstances, the direction of the later currents in 
the transportation of material may not always have coincided with that 
of the former ones ; and we may have diverging or cross ranges of 
mountains with higher summits, where the greater accumulation or the 
combined accumulations from several sources have taken place. 
It will not be easy to test this question immediately ; so preoccupied 
are the minds of observers with other views respecting mountain ele¬ 
vation, and so numerous are the circumstances that may lead astray the 
best intentions of seeing correctly. It is not many years since the belt 
of country between the Hudson river and the Atlantic was regarded 
as one great Primary mass. Later observers began to yield a little, and 
contented themselves with a Primary axis; and now we have the 
evidence derived from fossils occurring at intervals over much of the 
area between the Hudson and the Connecticut rivers, as well as from 
the geological structure of the country, that these rocks all consist of 
strata lying between the base of the Silurian and the beginning of the 
Coal measures ; while on the east of the Connecticut river, the crystal- 
*See the Reports of Nicollet, Fremont; of Emory, Abert, Cooke and Johnston*; of Captain 
Stansbury, Captain Marcy, Dr. D. D. Owen : Reports of Explorations and Surveys fora railroad 
route to the Pacific, Marcoit, Blake, Newberry and others : Emory’s Report on the United States 
and Mexican Boundary Survey, Geology, etc., by the writer. Also, results derived from Explorations 
on the Upper Missouri in 1853, made under my direction, by F. B. Meek and F. V. Hayden|. In 
addition to all these, may be cited the facts acquired by, or the results derived from, the observations 
of all the explorers of this mountain range. 
* Ex. Doc. No. 41, Thirtieth Congress : Notes upon the Minerals and Fossils, etc., by Prof. J. W. Bailey. 
f A communication made by the writer to the American Association.for the Advancement of Science, at the meeting 
of 1855. ( Not printed.) 
