56 NOTES ON THE 



now be protected by colored glasses or by a green veil. In consequence of 

 neglecting this precaution wlien I attempted to reach the crater of the peak of 

 Orizaba in September, 1856, 1 suffered severely for several days with snow blindness. 

 It is well to send four or five of the Indians ahead that they may tread steps into 

 the snow, or where the surface is hard, cut them in with a hatchet. By means of 

 these steps the ascent is rendered at once safe, easy and short, as, the average slope 

 being about 30°, about one foot is gained in height for every two feet of distance. I 

 found ice spurs and long iron-pointed sticks or boat-hooks entirely unnecessary, 

 only encumbering the traveller, and followed, in my second and tliird ascent of this 

 volcano, the example of the Indians, who use nothing but a common rude walking- 

 stick, notwithstanding that each one carries a load of from twenty-five to fifty 

 pounds on his back. I did not pass or see a single dangerous spot, and consider 

 myself very fortunate in not encountering any of those places, where " one slip of 

 the foot or a single false step would precipitate the wanderer into the fearful abyss 

 whicli yawns beneath him," sucli as some travellers, who ascended the mountain a 

 short time before I did, found on their road, although it must have coincided nearly 

 with the one I took. On the peak of Orizaba, however, and also on the Ixtacci- 

 huatl, I have seen crevices in the snow which might well prove fatal to the careless 

 mountaineer. 



A very unpleasant sensation is experienced in approaching the summit of a 

 high mountain, in consequence of the difficulty of breathing during tlie ascent. 

 It is not felt as much while walking as during the intervals of rest, which become 

 necessary every fifteen or twenty minutes, and is so much like choking, that the 

 traveller is sometimes impelled to tear the veil from his face and to throw off his 

 neckcloth to obtain air. 



But, although I have been five times on heights exceeding tliat of Mont Blanc — 

 between 16,400 and 17,400 English feet, and generally accompanied by eight or 

 more persons, I have never seen an instance of blood rushing from tlie nose, mouth 

 and ears, as observed by many travellers ; and my opinion is, that whenever it 

 occurs, the cause of it is more the exertion than the rarefied air. Neither have I 

 ever experienced the painful sensation in the limbs, often mentioned, and ascribed 

 to the relaxation of atmospheric pressure upon the joints. 



The slope of the snow-covered part of the volcano on its east and north side is 

 very uniform, and the surface is only slightly undulating, so that it approaches the 

 form of a regular cone. When half way up, the sulphurous odor with which the 

 air above is impregnated is sensibly perceived. 



On reaching the crater the snow-mantle breaks off abruptly, showing that here 

 (on the north side) its thickness does not exceed five, at many places scai'cely three, 

 feet. The sides of the crater at the place where it is entered, fall off with an incli- 

 nation of about 40° for the first hundred feet. The steep slopes are covered with 

 black volcanic sand of the same nature as that which covers the surface at the foot of 

 the cone. Above the sand project huge rocks of a very compact, dark gray or 

 black lava, most of which present a rounded surface, except where they have been 

 split after their formation. Thirty-two feet (perpendicularly) below the point where 

 the crater is entered, is an overhanging rock, against which the Indians, who carry 



