g2 FIELD CoLUuMBIAN MusEUM—GEOLOGY, VOL. I. 
ALTITUDES OF SNOW LINE AND LIMIT OF VEGETATION ON POPOCATEPETL. 









METERS. FEET. 
Height of snow line on the West reer 
Side, dalitiatyne. ate sate sare 3,700-3,800 Ay 20 Humboldt, 1803. 
Height of snow line on the West 404 
side, Deptemer., micas aa 4,500 14,764 | Humboldt. 
Height of snow line on the North 
siden DecémbBerwin ec heratt ae 4,400 14,436 | Felix and Lenk, 1887. 
. Height of snow line on the North be 
SETC sete om tees el er as eer aa 4,350 14,272 | Aguilera and Ordofiez, 
1894. 
Height of snow line on the South- 
east side, April.. nes 4,300 14,105 | Dollfus, 1865. 
Limit of vegetation, East side..... 4,180 13,714 | Dollfus. 
: North side.. 4,023 13,200 | Sonntag, 1857. 
elacaerinl A cs West side. . 3,845 12,615 | Gerolt, 1834. 
ap bas 2 SEAS Je: 3,869 12,694 | Glennie, 1827. 
Limit of trees, North side He ll 4,030 13,222 | Aguilera and Ordofiez. 
* Northwest side..... 3,039 11,939 | Sonneschmidt, 1770. 
<  “« — « South-southwest side 3,823 12,543 | Glennie. 
re Seeves SAW GG ASk: SLC Care eh ewe opens 3,980 13,048 | Dollfus. 

The advance over this part of the trail was very painful for the 
animals on which we were mounted, owing to the loose footing and 
rarefied air, and they could take but a few steps before they were . 
obliged to stop and rest. After a ride of somewhat more than an 
hour, the point called La Cruz was reached, and from here the ascent 
of more than three thousand feet, had to be made on foot. A 
rough, wooden cross erected at this point gives to the place 
its name of La Cruz. This cross is said by some to have been 
erected, in accordance with the Mexican custom, in memory of a 
man who died in the crater, while by others it is said to have been 
used as a shrine before which the sulphur miners in earlier times knelt 
to give thanks, after a safe return from their perilous journey to the 
crater.* The rough bosses of the lava stream project in this region 
above the smooth slope of sand with which most of the cone is cov- 
ered, and give a wild and desolate aspect to the scene. ‘The rocks 
are chiefly the red, slaggy breccias and grayish-black, compact andes- 
ites seen later at the northeastern edge of the crater. The close sim- 
ilarity observable in the rocks of these two regions is regarded by 
Aguilera and Ordojiiezt as sufficient proof that they belong to one and 
the same lava flow, the connecting area being supposed to have been 
lost through erosion or to be hid by the covering of snow and sand. 
Other observers, however, look upon the prominence of the lavas at 
this point, as well as the fact that a broadening of the stream is vis- 
ible as it descends the slope, as indicating that a lateral outburst 
*Felix and Lenk, of. ci¢. p. 24. 
tOZ. cit. p. 32. 
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