

‘ THE 
AMERICAN NATURALIST 
VoL. XXV. OCTOBER, 1891. 298. 


A SKETCH OF THE GEOLOGY OF SOUTH AMERICA. 
BY GUSTAV STEINMANN.? 
oy preparing a sketch of the geology of South America I feel 
obliged to add some explanatory remarks. This sketch’ ac- 
companies a map which forms a part of the second edition of the 
Physical Atlas of Berghaus (Gotha, Justus Perthes), which publi- 
cation will be finished at the end of this year. Besides many 
other maps, the geological part of this atlas has sketch- 
maps of all continents, which represent the actual state of our 
knowledge. In preparing the sheet of South America I was 
aided by many geologists who, like myself, had occasion to 
explore some parts of this continent, especially by Orville 
Derby for the part of Brazil, by Luis Brackebusch for the part 
of the Argentine Republic, and by many others. 
I thought it of some interest to the Association of North 
American Geologists to explain the main resemblances and dif- 
ferences which exist between the northern and the southern part 
of the great American continent, and to urge some remarkable 
points in the geological evolution of South America. 
I pass by the primordial rocks, very imperfectly studied as yet 
in South America. The Paleozoic rocks are better known, and 
offer great interest. By the investigations of d’Orbigny, Forbes, 
Kayser, Rathbun, Clarke, Orville Derby, and those made re- 
cently by Dr. Ulrich, of Strassburg, upon the rich collection of 
1 Professor of Geology in the hacen of Freiburg i, B. Read before the Geological - 
Society of ETUE August 25th, 1 


