75 • 



At the Ordinary Meeting holden on the same evening, John Clau- 

 dius Loudon, Esq., of Porchester Terrace, Bayswater • and Thomas 

 Copeland, Esq., of Golden Square, were elected Fellows of this So- 

 ciety. 



An extract of a letter was read from Lieutenant William Glennie, 

 R.N., dated Mexico, May 6th, 1827, entitled "The Ascent of Popo- 

 catapetl." 



Many contradictory reports having long existed respecting the 

 volcanic nature of this mountain, the author felt desirous of ascer- 

 taining its actual condition in person. 



The ascent commenced during the month of April 1827, from the 

 village of Ameca, situated in the province of Puebla, and near the 

 N.W. foot of the volcano, at an elevation of 8216 feet above the 

 level of the sea, and distant 1 4 leagues from Mexico. 



The author describes the sides of the mountain as thickly wooded 

 with forests of pines, extending to the height of near 12,693 

 feet, beyond which altitude vegetation ceased entirely. The ground 

 consisted of loose black sand of considerable depth, on which nume- 

 rous fragments of basalt and pumice-stone were dispersed. At a 

 greater elevation, several projecting ridges, composed of loose frag- 

 ments of basalt, arranged one above another, and overhanging preci- 

 pices 600 or 700 feet deep, presented formidable impediments to the 

 author's progress ; and, in one direction only, a ravine was observed 

 to pass through these ridges, having its surface covered with loose 

 black sand, down which fragments of rocks ejected from the crater 

 continually descended. 



After twelve hours of incessant fatigue the author gained the highest 

 point of the mountain on the western side of the crater, 1 7,884 feet 

 above the sea •. at which station the mercury in the barometer sub- 

 sided to 15*63 inches, and the temperature indicated by the attached 

 and detached thermometers, was respectively 39° and 33° Fahr. at 

 5 o'clock P.M., when exposed to the direct rays of the sun. The 

 plain of Mexico was enveloped in a thick haze, and the only distant 

 objects visible at that time, were the volcanoes of Orizaba and Iztac- 

 cihuatl. The crater of Popocatapetl appeared to extend one mile in 

 diameter, and its edges of unequal thickness descended towards the 

 east. The interior walls consisted of masses of rock arranged per- 

 pendicularly, and marked by numerous vertical channels, in many 

 places filled with black sand. Four horizontal circles of rock diffe- 

 rently coloured were also noticed within the crater ; and from the 

 edges of the latter, as well as from its perpendicular walls, several 

 small columns of vapour arose smelling strongly of sulphur. The 

 noise was incessant, resembling that heard at a short distance from 

 the sea shore during a storm • and at intervals of two or three mi- 

 nutes the sound increased, followed by an eruption of stones of va- 

 rious dimensions ; the smaller were projected into the ravine before 

 mentioned, the larger fell again within the crater. 



The sensations experienced by the author were analogous to those 

 usually felt by travellers at considerable elevations ; viz. weariness, 

 difficult respiration, and headache, the latter inconvenience having 



