72 PREFACE. 
present state of knowledge concerning the mountains in a form more 
accessible to English readers, would afford a means of stating the 
problems yet unsolved in regard to the structure and geology of the 
mountains and would aid travelers from our own country in making 
additional observations as opportunity afforded. The performance 
of this latter part of my task I have not been able to carry out in as 
comprehensive a manner as I wished, owing to inability to consult all 
the literature. The principal works, however, were at command. 
For courtesies shown, and assistance in my trip, I am indebted 
to many, but among these should be mentioned President E. E. Ayer, 
of the Field Columbian Museum; President A. A. Robinson, of the 
Mexican Central Railway; Mr. W. W. Blake, of the Two Republics; 
General Sanchez del Ochoa, of the City of Mexico, and Sefior Don 
Pedro de la Noriega, of Ameca. 
