2 
Classification of Rocks 
stone called chalk may, indeed, be mentioned as an excep¬ 
tion, being, so far as is known, peculiar to Europe, and 
principally to its western portion. If, then, the classifica¬ 
tion and arrangement of rock formations depended on 
their mineral characters alone, the task would be equally 
easy and uninteresting; since it would be enough to enu¬ 
merate the localities in which each variety of rock was to 
be found, and all would be done. 
When, however, we come to look on the rocks which 
form the crust of the globe as a great series of documents, 
containing within them each the history of its own for¬ 
mation, and unfolding, when studied together, the won¬ 
derful story of the changes which have taken place upon 
the globe, the remark of Humboldt ceases to contain the 
whole truth; and the geologist, in approaching a new 
country, feels the same interest as the reader, when 
opening a new volume of a delightful story. The kind 
of stone, indeed, may be the same as that with which he 
is already familiar; but this is merely as it were the type or 
the paper of his book, the matter upon which the story is 
impressed, or the covering in which it is enclosed. By 
examining the included organic remains, and the several 
relations of the rocks among themselves, he expects to be 
made acquainted either with the history of a period alto¬ 
gether new to him, or at least of transactions contem¬ 
poraneous with, and differing from, those he is already 
familiar with elsewhere. 
It has frequently happened that travellers, in hastily 
passing through new countries, have trusted to mineral 
characters alone,—have spoken of meeting with old red 
sandstone, or mountain limestone, merely because they 
have found stone resembling that which is to be found in 
those formations in Europe. Geological classification 
has, indeed, so much altered,—its principles and practice 
have become so much more enlarged and general within 
