210 Maclure on Geology. 
gested the first hint which afterwards led to the discovery of 
the marble. Doubts being entertained concerning some of the 
geological relations of those rocks, a letter was addressed to 
r. Maclure (then in Philadelphia) on the subject. His answer 
is subjoined. 
In giving it to the public, the editor takes a liberty which 
he hopes the respectable author will pardon, because_his pro- 
duction, although evidently never intended for the public eye, 
contains statements and opinions of no small importance to the 
young geologist, especially of this country. 
Geology, at the present day, means not a merely theoretical 
and usually a visionary and baseless speculation, concerning the 
origin of the globe; but, on the contrary, it is the result of actual 
examination into the nuture, structure, and arrangement of the ma- 
——- of which it is composed. It is therefore obvious, that 
: opinions of those men, who, with competent talent and sci- 
— have, with a direct reference to this subject, aie 
~~ countries, and visited different continents, are entitled 
minent respect. Saussure, by his scientific journeys among 
the s: (although a limited district) has given deserved cele- 
brity to his own name, and, if it were possible, has thrown a 
additional charm of attraction over those romantic and sublime 
regions. Dolomiew has made us familiar with the productions 
and phenomena of volcanoes, those awful and mysterious lab- 
oratories of subterranean fire. Humboldt has surveyed the ‘sub- 
limest peaks of both continents, and examined the structure of 
the globe amidst the valleys of Mexico and the snows of Chim 
borazo and Pinchinca; and Werner, with opportunities tach 
more limited, (confined indeed to his native country; Saxony 
but with astonishing sagacity and perseverance, deduced from 
he saw, a classification of the rocks of our globe, , which, 
although not perfect, has done immense service to the science 
of Geology. In this distinguished group (to which other impor- 
tant names might be added) Mr. Maclure has unquestioné bly@ 
right to be placed. Few men have seen so much of the st strac- 
ture of our globe, and few have done so much with such sina 
pretensions, His work on American Geology is noticed with © 
