VIEW OF THE COUNTRY. 87 



April IsL — We crossed the Uspallata range, and 

 at night slept at the custom-house, the only inhabited 

 spot on the plain. Shortly before leaving the mount- 

 ains, there was a very extraordinary view : red, 

 purple, green, and quite white sedimentary rocks, 

 alternating with black lavas, were broken up and 

 thrown into all kinds of disorder by masses of por- 

 phyry of every shade of colour, from dark brown 

 to the brightest lilac. It was the first view I ever 

 saw which really resembled those pretty sections 

 which geologists make of the inside of the earth. 



The next day we crossed the plain, and follow- 

 ed the course of the same great mountain stream 

 which flows by L uxan. Here it was a furious tor- 

 rent, quite impassable, and appeared larger than in 

 the low country, as was the case with the rivulet 

 of Villa Vicencio. On the evening of the succeed- 

 ing day we reached the Rio de las Vacas, which 

 is considered the worst stream in the Cordillera to 

 cross. As all these rivers have a rapid and short 

 course, and are formed by the melting of the snow, 

 the hour of the day makes a considerable differ- 

 ence in their volume. In the evening the stream 

 is muddy and full, but about daybreak it becomes 

 clearer and much less impetuous. This we found 

 to be the case with the Rio Vacas, and in the morn- 

 ing we crossed it with little difficulty. 



The scenery thus far was very uninteresting 

 compared with that of the Portillo pass. Little 

 can be seen beyond the bare walls of the one grand, 

 flat-bottomed valley, which the road follows up to 

 the highest crest. The valley and the huge rocky 

 mountains are extremely barren : during the two 

 previous nights the poor mules had absolutely no • 

 thing to eat ; for, excepting a few low, resinous 

 bushes, scarcely a plant can be seen. In the course 

 of this day we crossed some of the worst passes in 



