80 
GEOLOGY OF NORTH AMERICA 
The Sierra de Batuco and the mountains which limit the basins of the rivers San Miguel, Sonora, 
San Jose, de Cruz, in the State of Sonora, belong to the system of the Sierra Nevada. Their direction 
is likewise North and South, and they contain in their bosom veins of auriferous quartz, identical with 
those of California. 
13. Sierra of San Francisco and Mount Taylor system. — We have, at the 35° of latitude, from Soda 
Lake , which terminates the river Mohavee , near the Colorado of California , to the sources of the Ar- 
kansas and Canadian rivers, a volcanic belt running from West to East, and consisting of immense ex- 
tinct volcanoes, the two principal ones bearing the names of the Mountains or Sierra of San Francisco 
and Mount Taylor. 
The height of many of these volcanoes is considerable ; thus the principal cone of the Sierra of San 
Francisco is 15,000 feet, and Mount Taylor surpasses 10,500 feet. The lava streams and Secondary 
cones of all these volcanoes occupy a great surface; though they are actually extinct , and do not ap- 
pear to have been active for many ages. 
The current of lava covers in many places, particularly in the valley of the Rio Grande del Norte, 
the drift of the Quaternary epoch , and also the alluvium. A fact which seems to indicate for the re- 
lative age of this volcanic band, the end of the Quaternary period. 
More to the north, and following one of the lines of dislocation of the Sierra Nevada, we find, 
running North and South, on the meridian of 122° west of Greenwich , a line of volcanoes, most of which 
are still in a state of activity, especially Mount S' Helena, near the Columbia river in Oregon, and Mount 
Baker in Washington Territory. The age of this last volcanic belt appears to be the same as that of 
the belt of extinct volcanoes above-mentioned, so that we have a rectangular volcanic system, the two 
directions cutting at right angles, and yet both of the same geological age. This system appears to 
me to belong to that noticed by Elie de Beaumont as composed of three volcanic bands , forming a single 
tri-rectangular system. 
I have not yet found, with certainty, the system of dislocation which took place at the end of the 
Cretaceous period, and I am greatly disposed to adopt the opinion of Elie de Beaumont, who a long- 
time since pointed out in the Alleghanies, ruptures which should belong to this period. Those dislocations 
are found principally in North Carolina and Georgia. 
In closing this hasty and imperfect attempt at a classification of the mountains of a part of 
North America, I call the attention of Geologists to the relations existing between the different 
periods or groups of American strata , and the lines of dislocation and the elevations which tra- 
verse this great country. Here, as in Europe, the chains of mountains have intimate relation with 
each division of the chronological scale of stratified rocks. 
The fossil remains are the « medals of creation*, while the mountains are its colossal statues; 
with a collection of a certain number of fossils and minerals, one may write, and even stereotype, 
a chapter of the World’s history; but this chapter always begins with an immense capital letter, 
which is a chain of mountains. 
