OF NORTH AMERICA. 
87 
I have been reproached with being a stranger, and consequently not so well acquainted with 
American geology as a native. To introduce in this way the know-nothing doctrine into the judge- 
ment of a scientific work, is to say the least extraordinary, and not much in favor of the liberality 
of its authors. It is true that I was born a Frenchman, and educated at Paris, but I have led such 
a wandering life, that it is difficult to say to what nation I belong; so much so, that Roderick I. 
Murchison in his Siluria (page 411) calls me « a Swiss by birthn, probably owing to my intimate relations 
with Agassiz, Thurmann, Merian, Escher de la Linth, and other Swiss geologists. I went to 
America at the age of 24, and was so delighted with that fine country, its political and social 
institutions, and its people, that I renounced my nationality to make my abode in the New World, 
and if I am now in Europe, it is on account of my health, which obliged me to return for a time. 
The American Government honored me with an appointment as United States Geologist for an ex- 
ploration of the Rocky Mountains, and when opportunities occurred of requiring the Mexicans or 
the Indians to respect the Hag of the United States, I did not fail in my duty, and none of the 
officers of the Army with whom I served thought of qualifying me as a stranger. 
It is always disagreeable to he obliged to speak of one’s self, especially in a purely scientific 
work, but the repeated attacks made upon me by the most widely circulated American Scientific 
Journal, oblige me to my great regret, to break a silence, perhaps already too long, that my 
adversaries may take for submission to the insinuations and abuse, with w'hich they have honored 
me, during my absence from Bhston. 
I do not pretend to be more savant than the numerous other geologists who study North Ame- 
rica, and I do not wish to impose my opinions upon others. I have simply said what I have seen, 
without troubling myself whether my opinions were agreeable to this one or that. The sun shines 
for all, and I have tried during my roving life, as a travelling geologist, to look very sharply at 
all the stones, pebbles, and fossils I met on my road. 
I think every observer gives at least one fact, or one deduction conducive to the progress 
of geology , and it is only as such an observer that I present this Geological Map of a part of North 
America. 
The geology of the Prairies, the Rocky Mountains, California, and Oregon, is as yet so un- 
certain , that it is impossible to fix the exact limits of each formation. The map presents only an 
approximation to the geology of these countries ; I am only sure of the limits of the formations upon 
the line I have explored near the Sa"' parallel of latitude; north and south of this the limits of the 
colors are only approximative. 1 might have avoided coloring any part beyond my route; but I 
thought even a rough indication of this terra incognita would be useful. To obtain this I had re- 
course to published or manuscript observations of the officers of the United States Army, who had 
commanded expeditions to explore those regions; to the intelligence communicated to me by the 
celebrated guide Leroux, during five months of daily conversation upon the topography, orography, 
and the rocks w'ith which he was so familiar; and finally I have profited by my owm experience 
and the immense horizon that opened upon my view from the heights of the Rocky Mountains and 
the Sierra Madre. 
How far the attempt has been a successful one, it is very difficult, if not impossible, for an 
author to judge. I see in my map many faults, and many more imperfections and wants, and 
