1898 
Mount 
Orizaba 
gave me the opportunity to look abroad over the panorama which the ril¬ 
ing sun was changing in appearance at every moment. X noted on this 
mountain as on those near the City of Mexico that the vegetation ends 
without the appearance of any of those Arctic forms we find above timber 
line in the D.S. Ho red snow chore this. The trees became shorter and 
4- w. 
eh outer but merely straggle to vt& WjL’trfl 3,0 S 3 OX CtV? H3T X" 1. StilcL AOlld 
of ths .emtted thick#*s of low b VL0h&$ find afc triiacarliti# in most of our 
woods* Ho afhe Xor &mm jtmlpers at end of the lam bad at 
i 
timberline ©a Orizaba and also on 1st, at timberline were the nearest 
; . • t < a*- i- • 
approach. 
As day dawned 1 noted that the lower hills about us seemed obscured 
•*»« j ^ 
in fog or clouds and that it appeared to extend out over the valleys and 
I 
blot them out entirely. With my greater elevation and the aid of the 
sun I was now able to see that what X had Mistaken for fog or cloud ms 
nothing but the great dust stratum overlying the earth. 
At 8 o*clock only 2 or 3 cumulus clouds were to be seen far away to¬ 
ward the horizon. At 9 o*olock I had reached an elevation a little above 
Xu,000 feet and found, what I had noted both on Popocatepetl and Izt,,- 
t 
that the heavy dust and moke bearing stratum of the lower air was abrupt¬ 
ly limited at about 16,000 feet. Above spread e sky of the most intense 
turquoise blue I have over seen,- except on the summits of the other two 
peaks* This brilliant sky extended down unchanged in brilliancy almost 
to the very horizon of the dust layer* Far away to the wost, gleaming 
white in the sun, 1 could see the crests of Popocatepetl and Izt. rising 
into the clear air above the layer of dust,- but with all their bases 
below 16,000 feet concealed es effectually as though they were snowy is¬ 
lands rising Id the midst of a dun brown sea. 
As on ry former climbs, this strange limitation of the earth*s dusty 
air at 16,000 feet fonsed an upper horizon uribreken except by the white, 
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