MOUNTAINS AND THEIR ORIGIN. 99 
able, it lias been constantly heaving and falling ; 
and if we are not impressed by its oscillations, it 
is because they are not so regular or so evident 
to our senses as the rise and fall of the sea. The 
disturbances of the ocean, and the periodical 
advance and retreat of its tides, are known to 
our daily experience ; we have seen it tossed into 
great billows by storms, or placid as a lake when 
undisturbed. But the crust of the earth also has 
had its storms, to which the tempests of the sea 
are as nothing, — which have thrown up moun- 
tain waves twenty thousand feet high, and fixed 
them where they stand, perpetual memorials of 
the convulsions that upheaved them. Conceive 
an ocean wave that should roll up for twenty 
thousand feet, and be petrified at its greatest 
height : the mountains are but the gigantic waves 
raised on the surface of the land by the geologi- 
cal tempests of past times. Besides these sudden 
storms of the earth’s surface, there have been its 
gradual upheavals and depressions, going on now 
as steadily as ever, and which may be compared 
to the regular action of the tides. These, also, 
have had their share in determining the outlines 
of the continents, the height of the lands, and 
the depth of the seas. 
Leaving aside the more general phenomena, let 
us look now at the formation of mountains espe- 
cially. I have stated in a previous article that 
