HILL: GEOLOGY OF THE ISTHMUS OF PANAMA. 159 
main Cordilleran system of Mexico, which is the southern continuation 
of the Rocky Mountain region of the United States, abruptly terminates 
with the great scarp or “ abfall" of the so called Plateau a little south 
of the capital of the Republie, and that these mountains have no oro- 
graphic features in common with those of the Central American region 
lying to the south thereof. 
The trend of the two great North and South American Cordillera, 
the Rocky Mountain and the Andean systems, if protracted from their 
termini in Colombia and Southern Mexico respectively, would not con- 
nect through Central America, but would pass each other in parallel 
lines many hundred miles apart. The protracted Andes would pass 
through Jamaica and Eastern Cuba, and continue east of the longitude 
of the whole Appalachian system in the direction of Nova Scotia, A 
similar southward continuation of the North American Cordilleras would 
carry them into the waters of the Pacific, crossing the Equator far west 
of Central America and the South American continent. 
Jetween the widely separated termini of the main North and South 
American Cordilleras, as above defined, and extending directly across 
their trend at right angles to them, lies another great orogenie system 
of folding to which the term Antillean may be applied, and which has 
been of the utmost importance in giving to the Caribbean region its 
eonfiguration. It belongs to a system composed of corrugations hav- 
ing an east and west trend, which has never been appreciated by the 
geologist or geographer owing to the overwhelming proportions of the 
adjacent volcanic mountains. The corrugations extend along the 
Venezuelan and Colombian coast of South America, north of the Orinoco, 
the Isthmus of Panama, Costa Rica, and the eastern parts of Nicaragua, 
zuatemala, Honduras, Yucatan, Chiapas and Southern Oaxaca, and 
through the Great Antilles. Тһе mountains trending east and west are 
made up of granites, eruptives, and folded sedimentary rocks of Paleozoic, 
Mesozoic, and Czenozoie age in Guatemala and Southern Mexico;! of 
Mesozoic and Czenozoic age in the Antilles, Costa Rica, Venezuela, and 
Colombia, and of Czenozoie age in Panama. 
The two elongated submarine ridges stretching aeross the Caribbean 
from the Antilles to the Central American coast, between the Sierra 
Maestra range of Cuba and the Gulf of Honduras, and from Jamaica to 
Jape Gracias á Dios respectively, separated by the deep submarine valley 
known as “Bartlett Deep," have a suggestive and remarkable resem- 
blance to these east and west corrugations of the land. 
1 See further details in later pages of this report. 
