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hand, it must be admitted that the Lyellian nomenclature has 
now acquired such general, and indeed almost universal, cur- 
rency, that a change of names, which has no other object than 
the attainment of an impossible uniformity, is greatly to be 
deprecated. And there is, moreover, much to be said in favour 
of Ly ell’s names, not only on the ground of priority, but from 
the fact that they indicate the principles on which Lyell’s 
classification is based, and serve as a monument — the best 
possible monument, indeed — of the great advance in systematic 
geology which resulted from his labours. 
The value of the Lyellian method of classification is 
illustrated by the fact that in the third volume of the Principles 
its author was able to bring into more or less exact correlation 
the numerous and widely scattered Tertiary deposits which had 
been detected in various parts of the Continent. Since 1833, 
when this work appeared, Ly ell’s broad general outlines of the 
succession of events during the Tertiary epoch have been filled 
up in great detail by the labours of Prestwich, Constant 
Prevost, Hebert, Dumont, Sandberger, Beyrich, Hornes, Fuchs, 
Heer, Carl Meyer, and other investigators ; and in the applica- 
tion of Lyell’s method, its capabilities, and also its imperfections 
and shortcomings, have been brought to light by the test of 
practical experience. It will be instructive to notice the re- 
spects in which the Lyellian method, after being tried, has 
been found wanting. 
First among these, we may notice the circumstance that, as 
the acquaintance of geologists with the Tertiary formations has 
become more and more extended, deposits have come under 
their notice which it has been found difficult to refer to either of 
Lyell’s divisions, and which prove to constitute transitional 
formations linking two of them together. Thus the geologists 
of South Germany have shown that in the Vienna Basin the 
Miocene strata graduate so imperceptibly into the Pliocene, 
that they have been led to unite these two divisions, and call them 
the ‘ Neogene.’ But this class of objection cannot be regarded 
as especially applying to Lyell’s classification, for it is certain, 
from the very nature of the Gase, that whatever grouping of 
strata we may choose to adopt, certain deposits must be found 
which refuse to accommodate themselves to the artificial system. 
A more serious objection to Ly ell’s classification is based on 
the fact that at the period when he devised it, geologists were 
not acquainted with all the great representative faunas of the 
Tertiary epoch, and that since his time very important deposits 
have been discovered which cannot be referred to either of 
Lyell’s groups. The great brown-coal deposits of Northern 
Germany, which are now known to be of the ’age of the English 
Barton Clay, the highest member of the Eocene, are reached 
