16 INTRODUCTION. 
These two are embraced in Mr Lyell’s Recent Period, and 
here are found to exist the remains of those large animals, 
the Mastodon, Hippopotamus, Megatherium, Rhinoceros, &c. 
&c. To this Recent Period, belong the causes which 
are now so evidently in action, and with which we are fami- 
liar, such as the formation of coral reefs and islands, deltas, 
travertins, active volcanoes, &c. 
Viewing these changes, the facts of which have been 
established by the united exertions of geologists, within 
a comparatively short period, we reflect with intense in- 
terest on the disappearance from our planet of an im- 
mense number of species, numerous genera, and even 
some families! * 
The causes of the vast changes which it is evident to 
our senses, have taken place, are among the most inter- 
esting which have engaged the attention of mankind. 
Theories of all kinds have been promulgated, and little good 
has arisen from them, except that of the gradual develop- 
ment of facts, the accumulation of which has added to 
our stock of knowledge. It is said to be Fuchsel (a 
German geologist) who first asserted that the causes 
now in operation were sufficient to produce the changes 
observed in our strata. ‘Similar changes may now take 
place ; for the earth has always presented phenomena similar 
lo those of the present day.”* Such is the remarkable 
language of the author, published about seventy years 
since. Very recently, the theory of actual causes has 
been considered in England, by some of her ablest geolo- 
gists, as sufficient to satisfy the attentive observer. Mr 
Lyell may now be considered as the leader of this theory, 
and the mass of facts brought together in his admirable 
work, would seem to be enough to satisfy the most scep- 
tical. 
The rapid change which is now going on in the 
* De la Beche’s Geol. Man., p. 182, first English edition. 
