90 
HISTORY OF THE EARTH. 
appearance of the secondary strata especially, over the surface of 
the earth. In places where the pond is deep and free from drift¬ 
wood, the ice will subside regularly and uniformly along with 
the water, but if there is an island any where in the pond; or a 
large rock, or any thing of the kind, presents an obstacle to the 
regular subsidence of the ice, it will be seen broken and reposing 
upon the side of the rock or island, at a great variety of angles of 
inclination. 
This is the actual appearance of the secondary and transition strata. 
At a distance from any primitive mountain, as in the south-eastern 
part of England, they arc jiarallel to each other and nearly paral¬ 
lel to the horizon. In the neighborhood and on the sides of the 
Alps on the other hand, strata of the same kind ofrock occur in the 
utmost confusion and disorder, deranged and contorted in every 
direction and declining towards every quarter of the compass at 
every angle. 
The party which went out in the year 1S19-20, under the 
command of Major Long, to explore the country west of the Mis¬ 
sissippi, found a vast desert with a substratum ot sandstone 
stretching eastward from the Rocky Mountains through a dis¬ 
tance of more than 400 miles. The strata which constitute this 
formation of sandstone are sometimes nearly horizontal and 
sometimes considerably inclined. Near the mountains they are 
generally horizontal until we come to the very foot, where they 
are suddenly elevated in vast tables, into a position approaching 
the perpendicular. These appearances may be, accounted for, 
either on the supposition that the Rocky Mountains retain their 
primitive position, and that the whole body of the sandstone has 
sunk down from the higher level which it once occupied, and 
left the upright tables resting upon the sides of the mountains— 
or we may suppose that the sandstone now occupies the position 
in which it was originally consolidated, and that the Rocky Moun¬ 
tains have been forced up through it from below, deranging and dis¬ 
placing in their passage such of the superincumbent strata as were 
near enough to be eflected by them. One or the other of these 
conclusions appears to be unavoidable. 
There is evidence that in some localities the elevation,'in some 
the depression, and in others successive elevations and depres¬ 
sions of limited portions of the earth’s crust, have brought the 
rocks into the positions they now occup}’. 'I'hus on the south¬ 
ern coast of England, a stratum of marine origin is covered by a 
bed of black mould containing the petrified trunks of large trees 
and their stumps still standing erect in their native soil. Over 
these, fresh water, and higher still, other marine formations are ac¬ 
cumulated to a thickness of more than 2Q0'J feet. It is evident that 
the lower marine stratum must have been raised out of the sea, 
and a soil formed upon its surface, in which a forest took root and 
grew, and that the whole was afterwards for many ages the bot¬ 
tom of a deep ocean. It is now a second time dry land. Similar 
