HO HISTORY OF THE EARTH. 
these mountains, races of shell-fish came into existence, lived and 
died, accumulating the materials for tertiary strata of great ex- 
tent and thickness. The power which had elevated the Appenines 
now became active a second time, and Italy rose from the waters 
co-extensive with its present limits. Corresponding remarks 
may be made respecting the island of Sicily, in the southern 
part of which, the tertiary strata have been lifted to the height of 
3000 feet above the level of the sea. 
But when the shells from the Paris basin, from the sub-Ap- 
penine deposits, and from the south of Sicily, were compared 
with each other, and with recent or living species, a wide differ- 
ence is observed amongst them. In the Paris Basin, nearly all the 
species collected and determined, amounting to more than a thou- 
sand, (1238,) are now extinct, only 42 of the whole number being 
still living. The proportion of living species, is that of three and a 
half in an hundred, nearly. On the Loire, in the south of France 
near Bourdeaux, in Piedmont, and in the basin of Vienna, in which 
places there are tertiary deposits, the proportion is about eighteen 
in a hundred. In the sub-Appenine beds, from a third to a half of the 
species are still alive in the waters of the Mediterranean, though 
they are generally more numerous in seas nearer the equator, and 
attain a larger size there, indicating that a tropical climate, where 
its increase and development is greatest, is the appropriate hab- 
itat of the species ; and as the shells dug up in Italy are also larger 
than those that now cover the living animal in the Mediterranean, 
it is inferred that the climate of that country was formerly hotter 
than it is at present. Finally, the shells obtained in the southern 
part of Sicily, and sometimes on the tops of mountains of con- 
siderable elevation, agree, with few exceptions, with such as are 
found in the neighbouring seas at the present day. 
The general inference drawn from these facts, is, that the strata 
of the Paris basin, of the basin of Vienna, of the sub-Appenine, 
and of the south of Sicily, are not only not contemporaneous, 
but separated from each other by immense intervals of time. 
Between the era of the Paris basin and of that of Vienna, a period 
intervened during which not merely individuals, but whole spe- 
cies perished and became extinct, and others were created to sup- 
ply their places. A corresponding lapse of ages separates other 
tertiary deposits that differ in the same manner from each other, 
in the number of the living species they furnish. Nor does it 
appear that the genera or species which perished were swept away 
by any sudden and violent catastrophe. Either some unknown 
casualty brought the existence of the different races one by one 
to its close, or perhaps every species receives into its constitution 
at its creation, the seeds of decay and dissolution, along with the 
principle of life, so that the period during which it is to inhabit 
the earth, is circumscribed by certain definite limits. 
That geologists may be furnished with convenient names by 
which to mark and designate in their publications and communi- 
