Mineralogy and Geology. 261 
eg 5° 10° 15° 20° 25° 30°. 35° 474° 
O 25°30 25°11 25°20 25°51 25°73 25°90 26:34 26:92 2796 
C 25°30 aes 25° ae 25°50 25°68 25°92 26: aa 26° - 28°33 
work.—Z’ Institut, 1866, pp. 159, 165-168, G. H 
II. MINERALOGY AND GEOLOGY. 
. Geological explorations i in Northern Mexico; by A. Rimonn. sere 
riled from his notes, and prepared for publication, by J. D. W 
18 pp. 8vo. San Francisco, 1866.—We cite a few paragraphs from this 
valuable _ on _— geology of Northern oe : co, 
has become for its mines and ssieg. Resets Paine and how muc “ been 
written about it, it is surprising how little exact information has hitherto 
been obtained with regard to either its geography or geology. On com- 
ang = — published maps of the region in question, it will be 
seen a é how much they differ from each other in their delineations 
of nie "its, main topographical features, while the details are entirely 
wantin 
“The name of the ‘Sierra Madre’ is usually applied to the main range 
of mountains of this country, or the western border of the plateau goer 
Wwe go toward the a so, too, that of the valleys increases in that di: 
rection, the whole system of mountains and valleys spreading out in 
something like a fan shape. 
“Going north, the chain appears to sink gradually, penta deter- 
minations of altitude in northern Mexico are extremely few in number. 
It is eater that there is, in about latitude 32°, a depression of the moun- 
tain ranges which extends entirely across the continent, and which would 
enable the traveler to cross from the Atlantic to the Pacific, without nec- 
essarily surmounting an elevation greater than four thousand feet. The 
he highest, and the rarer point is said to 
the Cerro de Cuiteco, sixty leagues northéast of Jesus Farin on the 
? See Emory, in Mexican Boundary Report, vol. i, p. 41. 
Am. Jour. Sc1.—Szconp Szrres, Vou. XL, No. 125.—Sepr., 1966, 
34 
