that the narrower dimensions of the base are altogether owing to the immense accumulation of that material for centuries. On the upper edge of the crater, the snow—drifted by the winds—curled over the sharp ledges, but there were no indications of sulphur on the nearest rocks. Yet, in various parts of the rim, there were circular vents, from two to five inches in diameter, whence a sulphurous steam issued with a roaring sound, intermitting at intervals in strength and volume.
In order to examine these valves more closely, Mr. Von Gerolt descended about sixty feet into the crater, over masses of red porphyry. These contain much vitreous feldspar and approach the character of porous lava, while the immense wall of the opposite side seemed to be composed of different rock,—and, through the telescope, appeared in color of a violet gray, deposited in horizontal strata, resembling the material of the volcanic hill near Ayotla.
Our adventurers discovered no place by which they could reach the bottom of the crater, nor could they continue their examinations on the summit for any great length of time, as their sufferings were intense from the rarefaction of air, expansion of blood, a continual aching of their eyes and brows, and excessive debility. They conclude, from these facts, that the story related by Cortéz in his letters to Charles V., that Francisco del Montaño had descended into this gulf and "obtained sulphur from which they made their powder," is entirely inaccurate.
The silence at this immense height is described by Mr. Von Gerolt as "sepulchral," broken only at intervals by a subterraneous roar, like the sound of a distant cannonade, and the rattling of stones and masses of rock falling from the walls to the bottom of the crater. A similar sound is said to be frequently heard, even in the city of Mexico, in the direction of Popocatepetl. The frequent earthquakes that are felt in the Republic, heaving the whole land from the Gulf to the Pacific, from east to west, like the undulations of the sea, and manifesting themselves at all the points where there are indications of volcanic action on the surface, can only be accounted for by the hypothesis, that at a great depth, all these volcanoes (separated near their summits by transition and volcanic rock,) have a general communication over some vast central furnace, where the elements are in continual ferment.
It is related that, in the great earthquake of March, 1834, at half-past ten at night, the phenomenon was announced by regular oscillations of the earth from east to west, augmenting gradually until it became difficult to stand erect, while hundreds suffered as from the nausea of sea-sickness. The arches of the aqueduct, by which water is introduced into Mexico, (running in an easterly direction,) were split in their centers, while the one that comes from the north remained uninjured. This earthquake was experienced nearly at the same moment in Vera Cruz, St. Andres Tuxtla, Huatusco, (a village eight leagues from the volcano of Orizaba,) Jalapa and Puebla; but, singularly enough, it was not felt three leagues north of Huatusco, or at a few leagues both north and
