V. 

 THE ORIGIN OF MOUNTAINS. 



(1861.) 



The following pages are from a review entitled Some Points in American Geology, 

 which appeared in the American Journal of Science for May, 1861, and was devoted in 

 part to a notice of the remarkable essay which forms the Introduction to the third 

 volume of Hall's Paleontology of New York, from which numerous extracts are given 

 below. Eead in connection with Paper VII. of tire present volume, on Dynamical 

 Geology, it will serve to give a notion of the views of Professor Hall and the author 

 on the nature and origin of mountains. 



THE sediments of the carboniferous period, like those of earlier 

 formations, exhibit, towards the east, a great amount of coarse 

 sediments, evidently derived from a wasting continent, and are 

 nearly destitute of calcareous beds. In Nova Scotia, Sir Wil- 

 liam Logan found, by careful measurement, 14,000 feet of car- 

 boniferous strata; and Professor Eogers gives their thickness 

 in Pennsylvania as 8,000 feet, including at the base 1,400 feet 

 of a conglomerate, which disappears before reaching the Missis- 

 sippi. In Missouri, Professor Swallow finds but 640 feet of 

 carboniferous strata, and in Iowa their thickness is still less, 

 the sediments composing them being at the same time of finer 

 materials. In fact, as Mr. Hall remarks, throughout the whole 

 palaeozoic period we observe a greater accumulation and a 

 coarser character of sediments along the line of the Appalachian 

 chain, with a gradual thinning westward, and a deposition of 

 finer and farther-transported matter in that direction. To the 

 west, as this shore-derived material diminishes in volume, the 

 amount of calcareous matter rapidly augments. Mr. Hall con- 

 cludes, therefore, that the coal-measure sediments were driven 

 westward into an ocean where there already existed a marine 

 fauna. At length, the marine limestones predominating, the 



