248 Miscellaneous Intelligence. 
His scientific labors began early in life and were continued up 
to the present year. They were devoted especially to the study 
and description of recent shells and the fossil shells of the Tertiary 
were determined by cold intervals in the course of the earth’s 
progress, and he points out the great fact that the Mississippl 
depression, as it is often called, was a consequence of the elevation 
of the Appalachians on the east, and of the Rocky Mountain area, 
late in geological time, on the west. On the first of these points 
he remarks that “the theory of periodical refrigeration alone can 
explain the sudden extinction of whole races of animals and 
es. 
nd him 
lectual friends,” and watched with unfailing interest the progress 
of scientific discovery. 
