Principles of Geology. 11 
in rocks, and buried in mountains, far removed from the sea. To 
find the cause of this phenomenon was an object of interest, long 
before any settled system of geological observation and induction 
was thought of. The study of organic fossils was prosecuted with 
various success by different naturalists, but it was reserved for our 
own times to demonstrate their high importance in elucidating the 
history of the earth. Undoubtedly it is possible to acquire a com- 
petent notion of fossil plants and animals, without particular reference 
to geology ; but no one can be a geologist who disregards the natu- 
ral history of fossils. 
_ The slightest practical examination of rocks demonstrates that 
whilst some strata abound with these remains, others contain very 
few, and some are absolutely void of them. The absence of fossils 
was once used as a character of the primary rocks, but incorrectly ; 
for several of the secondary, and all of the independent rocks, are 
as destitute of fossils as granite and mica slate. Since, then, among 
the secondary rocks, some contain, and others do not contain, or- 
ganic remains, they may thus be sometimes distinguished. But 
when we consider the immense variety of organic remains, and learn 
that ina very limited district of England, many hundreds of species 
can be collected, and in the whole kingdom several thousands, it be- 
Comes evident that a more important branch of the inquiry remains : 
viz.—in what manner the different species are distributed in the in- 
terior of the earth. Whether, for instance, they are arranged ac- 
Cording. to §eographical position, as is partly the case with existing 
1 ©€8; OF according to the order of the different rocks, or mixed con- 
fusedly together, 
That they are not mixed confusedly together, is decisively proved 
by many cases like the following : the fossils of the chalk cliffs near 
Bridlington, are numerous and well known; so are those of the lias 
shale in the cliffs near Whitby ; and also those of the mountain lime- 
Stone near Skipton ; and on comparison, it becomes evident that no 
One fossil of the whole number is found in two of the strata enumer- 
ated! each of these three strata has its own peculiar fossils distinct 
from taose in the others. By prosecution of such comparisons, Mr. 
Smith discovered that organic fossils are distributed in the earth, not 
'0 Proportion to depth from the surface, nor even according to chem- 
eal Composition, but according to the order and succession. of the 
tocks. He has the great merit of establishing the facts, 
