Crust Movements. 
35 
at tlie bottom of the sea, with all its varied remains of 
a bygone age, was converted, for a season, into the 
surface of the earth, and became the theatre of animal 
and vegetable life; while in the latter case, the old 
surface of the earth, with its countless tribes of animals 
and plants — its fauna and flora, as they are called — 
was submerged beneath tho waters, there to receive 
in its turn broken-up fragments of a former world, 
deposited in the form of mud, or sand, or pebbles, or 
minute particles of lime. Nor is this all; it is but 
a singlo link in the chain of geological Chronology. 
W e are asked to believe that, in many parts of tho 
globe, this upward and downward movement has been 
going on alternately for unnumbered ages : so that the 
very same spot which was first the bed of the ocean 
was afterwards dry land; then the bottom of an 
estuary or inland lake; then, perhaps, once more the 
floor of the sea, and then tho dry land again; and, 
furthermore, we are assured that thousands and 
thousands of years may have rolled away while it 
remained in each one of these various conditions. 
But, from what source does that mighty power 
come, which can thus upheave the solid earth, and 
banish the ocean from its bed ? We are told, in reply, 
that this giant power dwells in the interior of the 
earth itself, and is no other than tho subterranean heat 
of which wo have already spoken. This vast internal 
fire acts with unequal force upon different parts of the 
shell or crust of the earth, uplifting it in one place, and 
