GEOGNOSY AND GEOLOGY. 919 
a 
motion, and, by successive subdivisions, furnishing the material for the indivi- 
dual bodies of our planetary world. ‘These masses of vapor must have pos- 
sessed a temperature sufficient to retain all the solid components in the 
gaseous condition. Such is the hypothesis of astronomy; geology takes it 
up at the time when the vapor is supposed condensed into a liquid, still 
molten mass, to which an ellipsoidal shape is given by a rapid rotation about 
an axis. In cooling, the earth becomes invested by a solid crust, upon which 
the aqueous vapors of the atmosphere are condensed. In proportion as the 
nucleus of the earth parts with its heat by radiation into space, must 
contractions of its volume take place; and the space between the inner 
kernel and the outer shell being thus of considerable amount, the incumbent 
mass breaks in and permits the access of atmospheric air to the fires below. 
The effects exhibit themselves in volcanic reaction, by means of which certain 
portions of land become elevated above the general level. A repetition of 
such depressions and elevations results in the elevation of entire continents 
with their mountain ranges and the collection of the great body of water in the 
interspaces. The ascending vapors from this water become condensed to 
clouds, fall in the form of rain, and, after partially saturating the more elevated 
regions, burst out into springs, whose combination produces rivers and lakes, 
all emptying continually into the great body of ocean, by a more or less circui- 
tous course. The sea, as well as the fresh water, acting on these continents, 
exerts a destructive influence upon the harder portions; and the finer particles 
resulting from their action are spread out and deposited as strata in some 
quiet bay or lake. ‘Smaller fragments, subdivided by concussion, attrition, 
atmospheric agencies, or other causes, are also carried down to form conglomer- 
ates. The masses arranged thus horizontally, and hardening by the incumbent 
weight or other influences into solid rocks, are elevated afresh, and new lines 
of demarcation are drawn between the waters and the dry land. We may safely 
consider such operations of aqueous and igneous causes as sufficiently capable 
of producing all the geological features of our globe. 
649 
