A SKETCH OF THE GEOLOGY OF MEXICO. 



Mexico is a country whose geology is very little known even 

 by its nearest neighbors. It nevertheless offers a wide range of 

 interesting problems. Its geology has been much misunder- 

 stood and this must be the excuse for presenting here a resume 

 of a portion of the very interesting report^ recently published 

 by the Geological Institution of Mexico. Aside from the itiner- 

 aries with detailed observations, the report includes a synopsis 

 of the geology of Mexico by the Director Sr. Jose G. Aguilera. 

 In the following pages is a very much abridged translation, or 

 abstract of Professor Aguilera's paper. The original is accom- 

 panied by a small scale map on which the geology is spread 

 over the areas left blank on the older map of Castillo^ and the 

 whole forms a notable contribution to the geology of the region 

 as well as being perhaps the best general summary of the present 

 state of our knowledge of the subject. 



Geographically Mexico may be considered as consisting of a 

 central tableland sloping to the north and northeast, and inclosed 

 between two ranges of mountains which are separated from the 

 oceans by strips of lowland narrowing to the south. The two 

 mountain ranges unite in the central portion of the country, ris- 

 ing above the lower land in the form of a colossal V, the 

 arms of which continue into the United States as the Rocky 

 Mountains and Sierra Nevada. The united range continues 

 south into Central America with the low tableland of Yucatan, 

 to the east rising thirty to forty meters above the sea. 



The central tableland or Mesa de Anahuac with an area of 

 about 666,000 kilometers and an average altitude of about 1700 



' Bosquejo geologico de Mexico, Bol. del Inst. Geol. de Mexico, Nums. 4, 5 y 6. 

 270 pp., S pi., map. Mexico, 1897. 



2 Bosquejo de una Carta Geologica de la Republica Mexico formada par dis- 

 posicion del Secretario de Fomento, i88g. 



384 



