762 The American Naturalıst. [August, 
The ascent of the peak was made on the 16th and 17th of April by 
Professor Heilprin and Mr. F. C. Baker, the rim of the crater being 
reached at 11.30 o’clock on the morning of the 17th, and the culmi- 
nating point early in the afternoon of the same day. Little difficulty was 
encountered in the ascent beyond that which is due to the incon- 
venience arising from the highly rarified atmosphere. The snow field 
was found to be of limited extent, and not more than from five to ten 
feet in depth, and was virtually absent from the apex of the mountain. 
The surprisingly mild temperature of the summit, 45 degrees Fahren- 
heit, rendered a stay of several hours in cloudland very delightful. 
THE Mountain OF ORIZABA.—With regard to the elevation of 
what is commonly supposed to be the second highest summit of the 
Mexican Republic, the peak of Citlaltepetl or Orizaba, the results of 
Professor Heilprin’s determinations show more marked variations from 
those of most of the earlier investigators, and more particularly from 
those of Humboldt. The latter determined the height of the moun- 
tain, by means of angles taken from near the town of Jalapa, to be 
17,375 feet, while a still earlier determination by Ferrer, in 1796, and 
recorded in the transactions of the American Philosophical Society, 
gave 17,879 feet. The latter estimate has been generally adopted by 
German geographers, and Humboldt himself has considered it more 
nearly representing the truth than his own measurement. The Mexi- 
can geographers, on the other hand, have adopted the measurement of 
Humboldt, or that which was obtained by the National Commissions of 
1877, and which indicated a height of 17,664 feet. 
Professor Heilprin, with three of his scientific associates and eleven 
guides, made the ascent of the mountain on the 6th and 7th of April, 
or ten days before the ascent of Popocatepetl. The last camp, at a 
height of some 13,000 feet, was left shortly before five o’clock in the 
morning of the second day, and after a difficult and continuous strug- 
gle of twelve hours through loose boulders, sand, and a much cut-up ice 
cap, the party—or rather the fragment which succeeded in holding 
out—finally reached the rim of the crater. 
A photograph was here obtained of the depression which marks the 
summit of this most symmetrical cone of the North American conti- 
nent. Professor Heilprin’s measurement, which was made at a point 
about 120 feet below the apex of the cone, indicates a total height of 
the mountain of 18,206 feet, or some 325 feet in excess of the measure- 
ment of Ferrer, and upwards of 800 more than that of Humboldt. 
The equal conditions of the atmosphere under which the measure- 
ments of both the peaks of Orizaba and Popocatepetl were made, and 
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