476 HARRY FIELDING REID 
Grewingk has apparently retreated about 600 feet in fifteen 
years. The next glacier to the northeast, though fed by the 
same fields, seems to have receded very little." 
Mt. Iztaccihuatl, in Mexico, has a snow cap from which a 
small glacier, the Porfirio Diaz or Ameca, protrudes (a second 
glacier has retreated to the snow-line). Sefior Ezequiel 
Ordofiez, of the Mexican Geological Survey, has put out signals 
to study its variations. Excellent descriptions and reproduc- 
tions of photographs of this glacier have been given by Dr. Oliver 
C. Farrington, of Chicago, with references to the literature.’ 
HARRY FIELDING REID. 
GEOLOGICAL LABORATORY, 
JoHNs Hopkins UNIVERSI1Y, 
June 28, 1808. 
«A map showing a part of this region, with corrections by Mr. Curtiss, has been 
published by Professor William H. Dall. Coal and Lignite of Alaska, U.S. Geol. 
Surv. 17th Ann. Rept., 1896, p. 786. 
2Qbservations on Popocatepetl and Iztaccihuatl, Field Columbian Museum, 
Publication 18; Chicago, 1897. Dr. Farrington has overlooked the interesting 
pamphlet of SENOR EZEQUIEL ORDONEZ, Notas acerca de los ventiqueros del Iztac- 
cihuatl; Memorias de la Sociedad Cientifica “‘Antonio Alzata;’’ Mexico, 1894. 
