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 Emort, Abkrt, Cooke and Johnston*; of Captain 

 Stansburt, Captain Marcy, Dr. D. D. Owen : Reports of Explorations and Surveys for a railroad 

 route to the Pacific, Marcoc, Blake, Newberry and others : Emory's Report on the United States 

 and Mexican Boundary Surrey, 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. HAYDENf. 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. 



t A oommanication made by the writer to the American Association for the Adranoement of Scicnoe, at the meeting 

 of 1855. ( Not printed.) 



