PREFACE. 
xi 
useful substances may be found. Thus, the traces of vegetables 
generally point out the vicinity of coal, whilst the remains of land 
animals show that, in general, in the places in which they are found, 
coal can exist but at prodigious depths. It is, therefore, hoped that, 
in future, the circumstance of particular fossils being found in 
certain strata, may be more particularly attended to : and whilst 
noticing the localities of fossils, it is recommended to mark the 
stratum, as well as the name of the place, in which they are found. 
The phenomena particularised in the latter part of this volume, 
yield some important knowledge respecting the structure of the 
planet which we inhabit. These facts would also supply, if it were 
needed, the strongest proof of the error of those who believe, that 
there has always been a succession something similar to what is con- 
tinually observed ; and that the human species have had, and will 
have, a uniform and infinite existence. With almost equal force will 
these phenomena oppose that system also, which considers the form 
and structure of the surface of this planet, as resulting from a regu- 
larly recurring series of similar mutations. 
The loss of whole species or genera, and the late creation of 
others, as is assumed in this work, are circumstances which strongly 
militate against both these hypotheses. It must, however, be ac- 
knowledged, that some accurate inquirers have doubted whether a 
single species has been thus lost. Bruguiere attempted to account 
for this apparent extinction of several species of shell-fish, by sup- 
posing that there are many genera, and even families, which live 
constantly in the lowest depths of the sea. These animals, which he 
termed Pelagian, being entirely out of the reach of man, can only, 
he supposed, become known to him by the mineralized remains of 
