108 FIELD COLUMBIAN MuSEUM—GEOLOGY, VOL. I. 
Pieschel* also observed what he believed to be a crater rim on 
the southeast flank of the mountain. As his opinion was based only 
on the appearance it presented as seen from Cholula, however, it 
can not be said to rest on very conclusive evidence. He also quotes 
from Humboldt a tradition of the Aztecs that the mountain at one 
time emitted smoke and ashes, but this is hardly satisfactory testi- 
mony. 
With regard to the areas of volcanic sand which occur upon the 
mountain, all observers agree that their source was probably Popocate- 
petl, since, on account of its proximity, a favorable wind would easily 
spread the sands over the slopes of Ixtaccihuatl. These volcanic 
products are, moreover, more numerous at the southern end, which 
is what might be expected if they came from Popocatepetl. This 
absence of any volcanic products originating in the mountain itself, 
the absence of any well-defined crater, at least so far as proved, the 
strikingly elongated form of the mountain, the prismatic columns 
which jut out all over its slopes, the homogeneous character of its. 
component rock and its coarse texture—all favor the supposition that 
the mountain may never have been, in any true sense of the word, a 
volcano, but originated as a great fissure eruption. The course of 
this fissure was obviously that of the Sierra of which it forms a part, 
and had the same direction as that which gave a partial vent to the 
lava and ashes of Popocatepetl. It can hardly be doubted also that 
the eruption took place prior to the formation of Popocatepetl. iS 
Heilprin states} that the mountain gives evidence of having been 
at one time much more elevated than it is to-day. What this evi- 
dence 1s, however, he does not indicate. 
The writer's trip to Ixtaccihuatl was made February 21-22, 
immediately after return from Popocatepetl. Horses and guides 
were procured at Ameca as before, and the party consisted besides 
myself of one mounted guide or caballero, and two Indian guides on 
foot. A pack mule was also taken to carry provisions and utensils. 
The route followed was essentially that indicated on Sonntag’s map, 
Pl. XVIII, it being the trail made by the zeveros or ice collectors who 
cut ice at the glacier and bring it down by mules to Ameca. The 
trail is also used bythe rancheros who live on the ranches scattered 
here and there over the flanks of the mountain, for bringing their 
products to market. After crossing the level plain on which Ameca 
is situated, the trail ascends rapidly, and the route is much steeper, 
comparatively, than that which leads up Popocatepetl. The brilliant . 
and varied flora, picturesque barrancas and beautiful cascades lend 

*Zeitschr. f. allg. Erdkunde, Bund. V, p. Igo. 
+O. cit. p. 258. 
