Physical geography. By Mary Somerville ...

CHAP. XII. GEOLOGICAL NOTICE. 131
size fall in cascades down this ledge between New York and the
Mississippi, affording scenes of great beauty.'
Both land and water assume a new aspect on the Atlantic Plain.
The rivers, after dashing over the rocky barrier, run in tranquil
streams to the ocean, and the plain itself is a monotonous level, not
more than 100 feet above the surface of the sea. Along the coast
it is scooped into valleys and ravines, with innumerable creeks.
The greater part of the magnificent countries east of the Alleghanies is in a high state of cultivation and commercial prosperity, with
natural advantages not surpassed in any country. Nature, however,
still maintains her sway in some parts, especially where pine-barrens
and swamps prevail. [The area of the thirty-one states which now
form the Union (1853) is 1,485,870 square miles, with an average
population of 15-48 to the square mile. The total area of the territory of the United States is 3,220,595 square miles, with an average population of 7-219 to the square mile. The areas of the great
lakes which lie on the north, and the bays which indent the Atlantic
and Pacific coasts, are not included in this statement. The total
population on the 1st of June 1850, according to the late census,
was 23,246,301; and of this number 19,619,366 are white. The
rate of decennial increase of the white population is 37-14 per cent.,
and the rate of annual increase of the total population is 3- per
cent.] The territory of the United States is capable of producing
everything that is useful to man, but not more than a twenty-sixth
part of it has been cleared. [According to recent statements,
1,400,000,000 acres of the public lands remain to be sold.] The
climate is generally healthy, the soil fertile, abounding in mineral
treasures, and it possesses every advantage from navigable rivers
and excellent harbours. The outposts of Anglo-Saxon civilization
have already reached the Pacific, and the tide of white men is continually and irresistibly pressing onwards to the ultimate extinction
of the original proprietors of the soil-a melancholy, but not a solitary, instance of the rapid extinction of a whole race.
Crystalline and Palsezoic rocks, rich in precious and other metals,
form the substratum of Mexico, for the most part covered with plutonic and volcanic formations and secondary limestone; granite
comes to the surface on the coast of Acapulco, and occasionally on
the plains and mountains of the table-land. The Rocky Mountains
are mostly Silurian, except the eastern ridge, which is of stratified
crystalline rocks, amygdaloid and ancient volcanic productions. The
coast-chain has the same character, with immense tracts of volcanic
The author is indebted to the' Physical Geography of North America,'
by H. D. Rogers, Esq., and to the very interesting' Travels' of Sir Charles
Lyell in the United States, for the greater part of what she has said on tho
Physical Geogrta.phy and Geology of that portion of the New World.