294 The American Geologist November. 1905 
investigation, and all necessary appliances for geologic re- 
search. The museum is especially well equipped with a 
large collection of nicely trimmed rocks and thin sections 
corresponding. ( Possibly there is no better place than 
Mexico for the study of variations in rhyolitic and andesitic 
outflows, and the Instituto Geologico keeps its doors open 
to scientists who desire to study there. The staff of the 
Institute at present consists of Jose G. Aguilera, appointed 
director on the death of Castillo, Ezequiel Ordonez, sub- 
director and petrographer, Emilio Bose, Carlos Burckhardt, 
Juan D. Villarello, E. Angermann, T. Flores, R. Robles, S. 
Truax, and A. Villafana, geologists, R. Santillan, secretary, 
F. Roel, and V. de Vigier, chemists. 
The Institute has an interesting and in some respects 
unique field for investigation. The larger portion of the 
sedimentaries and older crystalline rocks in Mexico are cov- 
ered by great masses of recent products of volcanic activity 
such as ashes, andesitic and basaltic outflows. The Insti- 
tute has a very complete collection of these jocks which 
have quite thoroughly been worked out from a petrograph- 
ical standpoint and presented to the public through its ex- 
cellent bulletins. Its investigators plan in the near future 
to discuss more completely the chemical relations of the 
outflows and doubtless valuable additions will be made to 
our knowledge of the differentiation of volcanic magmas. 
Volcanic craters are found everywhere, some in the state of 
activity (Colima) others possessing but faint traces of their 
former power (Popocatepetl). Even within less than two 
hours ride from the city of Mexico groups of volcanoes may 
be studied where crater cones rise but a few hundred feet 
above the level valley of Mexico (Sierra de Catarina.) 
These present variations from pure cinder cones (Las Cal- 
deras) to cones from the crater of which more liquid mate- 
rial has escaped (Cerro de Ixtapalapa). Thus a more ideal 
spot for the investigation of at least one phase of geology 
could hardly be imagined. 
Following is a list of the publications of the Institute: 
Num. 1. — Fauna Fosil de la Sierra de Catorce, por A. del Castillo 
y J. G. Aguilera.— 1895.— 56 pp., 21 1a.m. 
Num. 2. — Las Rocas Eruptivas del S. O. de la Cuenca de Mexico, 
por E. Ordonez. — 1895. — 46 pp., 1 lam. 
