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University of California. 



[Vol. 2. 



styled the Department of Panama, a strip of land about 400 miles 

 in length and 40 to 120 miles in width, with a probable average of 

 about 75 miles, is too large and diversified to be handled as a unit, 

 and may conveniently be divided into sections. It is the middle 

 section, characterized by high, abrupt mountains, peculiar rounded 

 hills and low plains, extending from the canal in a general west- 

 southwest direction to a distance of about 150 miles from Panama, 

 that is the subject of this paper. About 100 miles southwest from 

 Panama, the broad Peninsula of Azuero projects southward about 

 60 miles from the main body of the Isthmus. It is the oldest part 

 of the Isthmus country. West of it the coast is very irregular, 

 being indented by many bays, some of which are long and narrow 

 and beautiful examples of " drowned valleys." Off the southern 

 coast are many high mountainous islands. 



The chief section which I examined extended across the widest 

 portion of the Isthmus from Punto Mariato, the southwestern 

 extremity of the Peninsula of Azuero, till within five miles of the 

 Caribbean Sea, or directly through the center of the largest tract 

 of the Isthmus marked on recent maps as " unexplored." This 

 was directly across the strike of the strata, and it is believed that 

 all the principal formations developed in the district were seen, and 

 the geological history is known with a reasonable degree of com- 

 pleteness. As Mr. Hill found, it is the general rule on the Isthmus 

 that the formations become newer from south to north. 



TOPOGRAPHY. 



From the head of the Bay of Parita, 90 miles west-southwest 

 from Panama, there extends westward along the Isthmus a distance 

 of about 50 miles and over a width averaging about 20 miles, the 

 most beautiful peneplain of small extent which I have ever seen. 

 Nearly all parts of it must originally have been a perfectly base- 

 leveled plain dotted with many monadnocks from 50 to 500 feet in 

 height. Around the head of the Gulf of Montijo and near the 

 foot of the mountains north and west of Santiago the plain is much 

 dissected by canon valleys of no great depth and often of consider- 

 able width. The interstream portions are llanos, or grassy plains, 

 and on them live a large part of the inhabitants of the Isthmus. 



