XV r/XNACLES OF SNOW 347 



Tupungato, the whole clothed with unbroken snow, m the 

 midst of which there was a blue patch, no doubt a glacier ; — 

 a circumstance of rare occurrence in these mountains. Now 

 commenced a heavy and long climb, similar to that up the 

 Peuquenes. Bold conical hills of red granite rose on each 

 hand ; in the valleys there were several broad fields of perpetual 

 snow. These frozen masses, during the process of thawing, 

 had in some parts been converted into pinnacles or columns,^ 

 which, as they were high and close together, made it difficult 

 for the cargo mules to pass. On one of these columns of ice 

 a frozen horse was sticking as on a pedestal, but with its hind 

 legs straight up in the air. The animal, I suppose, must have 

 fallen with its head downward into a hole, when the snow was 

 continuous, and afterwards the surrounding parts must have 

 been removed by the thaw. 



When nearly on the crest of the Portillo, we were enveloped 

 in a falling cloud of minute frozen spicula. This was very un- 

 fortunate, as it continued the whole day, and quite intercepted 

 our view. The pass takes its name of Portillo from a narrow 

 cleft or doorway on the highest ridge, through which the road 

 passes. From this point, on a clear day, those vast plains 

 which uninterruptedly extend to the Atlantic Ocean can be 

 seen. We descended to the upper limit of vegetation, and 

 found good quarters for the night under the shelter of some 

 large fragments of rock. We met here some passengers, who 

 made anxious inquiries about the state of the road. Shortly 

 after it was dark the clouds suddenly cleared away, and the 

 effect was quite magical. The great mountains, bright with 

 the full moon, seemed impending over us on all sides, as over 

 a deep crevice : one morning, very early, I witnessed the same 

 striking effect. As soon as the clouds were dispersed it froze 

 severely ; but as there was no wind, we slept very comfortably. 



The increased brilliancy of the moon and stars at this eleva- 

 tion, owing to the perfect transparency of the atmosphere, was 



' This structure in frozen snow was long since observed by Scoresby in the 

 icebergs near Spitzbergen, and lately, with more care, by Colonel Jackson (/oiirn. of 

 Geograph. Soc. vol. v. p. 12) on the Neva. Mr. Lyell (Principles, vol. iv. p. 360) 

 has compared the fissures, by which the columnar structure seems to be determined, 

 to the joints that traverse nearly all rocks, but which are best seen in the non- 

 stratified masses. I may observe that in the case of the frozen snow the columnar 

 structure must be owing to a "metamorphic " action, and not to a process during 

 deposition. 



