662 REVIEWS 
much to our knowledge of tropical America. Some of the geographic” 
features which characterize the region have been briefly described by 
the author in earlier publications, but the geological results of the 
reconnaissance have not before been published. So far as practicable, 
Mr. Hill’s conclusions are stated in his own words. 
In the first place, emphasis is laid upon the independence of the 
North American, Central American, and South American orogenic 
systems. The Cordilleran system of North America ends in Mexico, a 
little south of its capital city. The Andean system of South America 
has its northern terminus east of the Isthmus of Panama, and has no 
genetic connection with the mountain ranges of the north coast of 
South America. If the Cordilleran and Andean systems were extended 
southward and northward respectively, they would pass each other in 
parallel lines hundreds of miles apart. The extension of the Andean 
system would lie not only east of the Cordilleran, but even east of the 
Appalachians, while the extension of the Cordilleran system would lie 
in the Pacific, far west of the South American coast. 
Between the termini of these orogenic systems, with a trend at 
right angles to both, lies a third system, called the Antillean. It is this 
system of mountains which has determined the major topographic 
features of the Antillean region. The system includes the east-west 
ranges of the north coast of South America, those of the Isthmus, 
Central America, southern Mexico, and the Great Antilles. In the 
Caribbean sea, two east-west submarine ridges, separated by the 
Bartlett Deep, show that the east-west trend of the crustal corrugations 
of this region affect the sea bottom as well as the land. Like the 
greater systems to the north and south, the Antillean system is com- 
posed of folded sedimentary rocks, plus volcanic intrusions and ejecta. 
While each of the major orogenic systems dominates a continental 
area, the Antillean system ‘‘ constitutes a mountainous perimeter sur- 
rounding the depressed basin of the Caribbean.” 
The primary geographic features of that part of the continent 
dominated by the east-west system are 1°, a volcanic plateau near the 
Pacific coast along the western termini of the ranges of the Antillean 
system, and 2°, the lower but mountainous area facing the Caribbean, 
consisting of folded beds of sedimentary rock, associated with igneous. 
To the north, the western termini of the Antillean ranges are buried 
by the volcanic rocks, but on the Pacific side of Panama, the Antillean 
ranges continue across the land area. 
