1890.] Geography and Travel. 761 
General Notes. 
GEOGRAPHY AND TRAVELS. 
Mexico.—In a communication made to the Academy of Natural 
Sciences of Philadelphia, at a recent meeting, Professor Heilprin 
placed on record his barometric determinations of the heights of the 
four loftiest summits of the Mexican Republic,—Orizaba, Popocatepetl, 
Ixtaccihuatl, and the Nevado de Toluca, From these it would appear 
that considerable corrections will have to be made in geographies of 
the recorded heights of these far-famed giants of the South. All the 
observations were made by means of a carefully tested aneroid barome- 
ter, and the data computed from almost simultaneous observations 
made at the Mexican Central Observatory of the City of Mexico, and 
from barometric readings made at the sea level at Vera Cruz. The 
The equable condition of the atmosphere at the time these observa- 
tions were made rendered the possibility of the occurrence of possible 
errors of magnitude almost 2. 
HEIGHT oF PopocaTEPETL.—The height of Popocatepetl, com- 
monly accepted as the highest peak, was recorded by Alexander 
von Humboldt in 1804 as 17,720 feet. Several measurements have 
been made since the date of the grigonometrical observations of 
the distinguished German traveler, and with results varying from 
17,200 feet to somewhat over 18,000 feet. Professor Heilprin’s 
measurements give 17,523 feet, or 200 feet less than the estimate of 
Humboldt, as corrected by his astronomical associate, Oltmanns. The 
significant fact, however, pointed out, that while geographers have 
almost universally accepted Humboldt’s determinations and figures, 
they have neglected to take account of the newer data which have 
been made possible through the leveling of the Mexican Railway, 
which was constructed a few years since. These show that the esti- 
mate of the elevation of the City of Mexico (7,470 feet) and of the 
adjoining plateaus, which have served as a basis for most of the angle 
measurements of the mountains, have been placed 123 feet too high. 
Allowing for this excess, a striking correspondence is established 
between the early measurements and those obtained in the spring of 
the year by the Philadelphia expedition. 
Am. Nat.—August.—5. 
