YOLCANO rOPOCATEPETL AND ITS VICINITY. 



59 



hatchet by which to descend. Our guide, whilst engaged in this work, at one 

 time lost his footing, and slid down about thirty paces before he succeeded in 

 stopping himself. 



The horizontal part of the bottom of the crater is covered with snow, above 

 the surface of which rise only a few large boulders. In February, I noticed on the 

 northeast side, at a place where the snow was wanting, some water of a bluish- 

 white color and a sour taste. In June this water had disappeared, and the surfece 

 was covered uniformly with snow, except in the vicinity of the chimneys, called 

 by the guides " respiradores." These exhibit the last, feeble evidence of the former 

 activity of the volcano, but its main throat has been so effectually choked up by 

 the rubbish, which has fallen into it, that at the lowest and central part of the 

 bottom no vapors issue. The present vents are a little way up the slope, and 

 from the two largest of these, one on the east, the other on the south side, rise 

 ■\olumes of vapor which extend to the edge of the crater, and sometimes in clear, 

 calm weather are seen above it. The noise of these jets may be heard at the top 

 of the crater, where it sounds much like the roaring of the wind, which may 

 have given rise to the belief common among the Indians, that a passage exists 

 between the crater and the surface of the cone near the top of "Pico del fraile," 

 through which the wind whistles. At the " respiradores" the steam issues from 

 the crevices between the stones, which, as Avell as the sand in their vicinity, are 

 covered with crystalline sulphur. 



The principal vent on the south side is about thirty feet in diameter, and {ill(>d 

 up with stones of all sizes, which are entirely encrusted with sulphur, and decom- 

 posed by its action to such a degree, that small pieces of them may be crumbled to 

 powder between the fingers. The large vent to the east does not cover so much 

 ground, but the steam issues under a higher pressure ; stones of eight or nine 

 inches in diameter, when cast upon one of the crevices, through which the vapor 

 escapes, are thrown back with such force as to fall to the ground several feet from 

 the opening. When we removed one of the larger stones from the vent, by the aid 

 of a long pole, sand, small stones, and sulphur, which had been covered by it, were 

 thrown up more than ten feet into the air. We tried also to measure the tempe- 

 rature of the vapor issuing from the "respiradores," but the thermometer being 

 graduated only to 160° F., burst from the heat, which exceeded this temperature. 



There is not much sulphur seen in the crater except near the vents, where it is 

 precipitated from the vapor and deposited on the rocks and the ground. This may 

 be accounted for by the fact that the falling stones and the debris, which is con- 

 stantly renewing the surface of the bottom of the crater, must certainly cover any 

 old beds of sulphur which may exist. The vapor which escapes consists of steam, 

 highly charged with sulphur in the form of sulphuretted hydrogen and of free 

 sulphur in vapor. Very little sulphurous acid issues, although this acid as well as 

 sulphuric is found in the air of the crater, as is proved by the sour taste of the 

 icicles and by incrustations of sulphate of lime on some of the rocks. As already 

 mentioned, the air not only in the crater, but outside half way down the cone, is 

 impregnated with sulphur, proving that a very large quantity of it is discharged. 



At the time of our explorations, in June, there was a cloud resting on the top 



