4 On the Physical Geology of the United States, Sc. 
joining valleys, salt water has been found, containing the same 
impurities as the waters of the ocean.* This salt water, on ac- 
count of its greater specific gravity than common water, might 
be expected to remain, filling the pores and vacuities of the rocks, 
the particles of which had been deposited in the bottom of the 
ocean. 
A minute examination of the sedimentary rocks, shows that 
they are composed of the fragments and comminuted grains of 
older and well known rocks, which have been washed away and 
deposited far from their original situations. 
Whence has this immense mass of fragments of older rocks 
been derived, that is found to have been deposited over this vast 
area in the United States? Are there any causes known, ade- 
quate to explain its origin? 
It may be said in answer, that there are data known from 
which we may reason with a probability of attaining an approxi- 
mation to truth. This subject is one that has scarcely been 
broached, and the causes that will be adduced as having proba- 
bly produced the transportation and deposition of a mass of such 
great thickness and extent, are such as may have been equally 
active on other parts of the earth’s surface. 
Before entering fully into this subject, it is necessary to con- 
sider some of the dynarnical causes that may have had an influ- 
ence in the production of the numerous and extensive sedimen- 
tary deposits upon the surface of the globe. 
Ist. It is generally admitted that the earth is a cooling body ; 
at least that its surface hasa much higher mean temperature than 
the regions of space in which it performs its revolutions around 
the sun; that the temperature increases rapidly from near its 
surface towards its centre ; and that it loses more caloric by ra- 
diation than it receives from the sun ;—in all which respects it is 
in the state of a cooling body. 
2d. Cooling bodies diminish in volume. 
3d. Bodies revolving on axes if diminished in volume, the 
quantity of matter remaining constant, revolve with increased 
angular velocities. 
* [have found bromine and iodine in several of the salt springs of Ohio. I have 
lately made some quantity of salts of bromine, and separated the pure bromine 
from the bittern of the salt springs near Athens, Ohio. The usual saline sub- 
stances of bittern are found in these springs except sulphates. 
