Actions of Volcanoes. 283 
forming their own habitations, have, in the progress of time, 
generated mountains ; as we may safely say, when we examine 
the enormous strata into which they enter as principal and con- 
stituent parts. 
Still, however, these do not make that impression on us 
which they ought; because, seeing these rocks as we do, mixed 
with others, long deserted by the sea and by their former inha- 
bitants, and now divested of all marks of life, and except to the 
eye of a geologist, of all indications of their former origin, we 
are apt to pass them by, and think that the surface of the earth 
might haye been nearly the same had these animals never 
existed, or had they remained at the bottom of that ocean 
where they lived and died. But when we trace this very act in 
its progress; when we follow with our eyes the increments 
which the land is actually undergoing in consequence of the la- 
bours of submarine animals, we receive a very different impres- 
sion respecting their importance ; and, in watching the hourly 
formation and increase of the coral islands, begin to be more 
sensible of the vast importance of this race of beings, and 
of the immense changes which all the marine tribes must 
have produced on the chemical nature, as well as on the 
structure and disposition, of the superficial or more recent 
strata. 
With respect to the operations of shell-fish, we know that 
they are now forming immense strata under the waters, just as 
they must have done in times long past, and before they could 
have produced the rocks which we now behold above the ocean. 
Whether these are ever destined to rise above the sea, or when 
that may happen, we cannot even conjecture; although, were 
we to reason from analogy derived from past events, we should 
conclude it was probable, unable as we are to assign the mode 
in which such an event is to be brought about, Should it hap- 
pen, new calcareous strata will be found on the surface of some 
future earth, and the fossil remains of those days will be 
what were the living species of our own. 
But when we examine the operations of the coral animals, we 
find in them that which we cannot in those of the shell-fish. In 
