TOPOGRAPHIC ELEVATIONS. 215 
were often violently precipitated either against masses of rocks, or to the 
very verge of precipices, from which they only saved themselves by the 
firmness of their nerves and the strength of their iron-shod staves. At 
length, however, after several yery narrow escapes, they reached the limit 
of the forest, and in a few days returned to Mexico in excellent spirits. 
.By the failure of the Indians to ascend with them to the summit, they 
were unable to make many experiments, for which the great scientific 
acquirements of Mr. Von Gerolt so highly qualify him. In addition to 
this, the barometer, which had been slung on the back of Mr. Egerton's 
servant, was broken by a fall ; so that (as far as measurements were con- 
cerned,) the expedition was entirely fruitless. I have, however, compiled 
from the notes of two other parties, the following statements, which are 
interesting, as affording the most accurate dimensions of this remarkable 
volcano : ' 
Mr. Berbeck, who ascended on the 10th of November, 1837, gives the 
elevation of Popocatepetl, above the Valley of Mexico, at 10,382 feet. 
Mexico is above Vera Cruz, according to Humboldt, - 7,470 
Whole height of volcano above the sea, - . - 17,852 
Mr. Glennie, who ascended 20th April, 1837, gives the elevation of 
Popocatepetl, above the Valley of Mexico, at - - 10,413 feet. 
Mexico above Vera Cruz, according to Humboldt, - 7,470 
17,883 
By a series of observations, made at Vera Cruz in 1828, the opinion is, 
that, the true height of Mexico above Vera Cruz, or in other words, above 
the level of the sea, is 7,548 feet, which, added to their elevations above 
the Valley of Mexico, will give us, for 
Berbeck, - - - - 17,930 feet. 
Glennie, - - 17,961 
While Humboldt, (who gives his by trigonometrical ob- 
servations,) .-...-.. 17,715 
The limit of all vegetation, according to Glennie, is - 12,693 
Pico del Fraile, - - 16,895 
Limit oi pines, • - - • - - - . 12,544 
In November, 1827, the thermometer, at the summit, was 22° of Fahr. 
and in April of the same year, 33°. 
At the limit of vegetation, Mr. Von Gerolt found, at 6 p. m., the precip : 
of moisture, by Daniell's hygrometer, 36° Fahr. on the interior ther- 
mometer; and at 50° in the atmosphere. Water boiled at 194° Fahr. 
Barometer, 19.12, English. Temperature, 48° Fahr. Correspond, 
ing observations, made in Mexico, gave 23.071 English inches, from 
which we deduce a height of - - - 5,144 English feet. 
To which add 7,548 
12,692 
