450 Geological Society. 



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 j 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 

 been first perceived at a height of 16,895 feet. Tobacco smoke and 

 spirituous liquors were also found to produce an unusually rapid eU 

 feet upon the sensorium. 



At the same meeting a letter was read from J. B. Pentland, Esq., 

 addressed to W. H. Fitton, M.D. P.G.S., respecting the fossil re- 

 mains of some animals from the N.E. border of Bengal. 



The author has discovered among the mutilated fragments of bones* 

 obtained from the tertiary deposits on the Bramahpootra River in the 

 small state of Cooch-Behar, — presented to the Society some years ago, 

 by David Scott/ Esq., and referred to in a former volume of the 

 Transactions *, — the remains of four distinct species of mammalia, 

 making an interesting addition to the list already published by Mr. 

 Colebrooke, viz. — 



1. A species of the genus Anthracotherium of Cuvier, which the 

 author proposes to distinguish by the name of A. Silistrense, — a spe- 

 cific denomination derived from one of the many names by which the- 



* Geol. Trans. 2nd Series, vol. i. p. 135. 



great 



