190 
several hundred feet above the road at the highest part of 
the pass to which it gives its name, consists of the latter 
rock, enclosing large rolled masses of porphyry. On the hills 
that we passed in the morning, although at a less elevation, 
there were no shrubs, the cold wind that sweeps unobstructed 
over the smooth sward, being inimical to the growth of 
young plants, which, on the contrary, find shelter among 
the masses of rock on the ascent to La Viuda, where stunted 
shrubs are very common, 
The pass of La Viuda is said to be 15,000 feet above the 
level of the sea.* On gaining the summit, a league from 
the bottom of the mountain, we came upon a more open 
country than we had seen since the commencement of our 
journey, though the prospect was still somewhat limited, the 
lowest situation being, of course, chosen for the road, from 
which we only had a partial view of the higher mountains 
in the distance, covered with perpetual snow. We descended 
very gradually among low ranges of black limestone, with 
impressions of shells; a yery extensive formation in this part 
of the Andes, The skirts of the hills, and the little vallies 
and tracts of level ground between them, were covered with 
verdure, and the deeper hollows were occupied by lakes 
the water of which was of a dark blue colour, more intense 
than that of the waters of the ocean; in some of them, the 
deeper tint was varied by patches of bright turquoise, from 
the bottom being of a whitish colour, and the water less deep. 
We: bad long passed the region of trees, and even shrubs 
had disappeared. The most conspicuous plant was à low, 
spreading Cactus, in large patches among the rocks; being 
: covered with abortive spines like white hairs: it had, at ? 
distance, exactly the appearance of wool. Near La Viuda, 
L observed Culcitium rufescens, and a species of Trevoas ? 
= yor 
De E 
* Tam sorry to find that I have mislaid a memorandum of the altitudes of 
x isa places between Lima and Pasco; they were measured barometri- 
A by e Mariano Rivero, and published in Lima, in the Mémorial de le 
PN "einn = ei. J m one of the conductors. As tbe list includes 
m ‘of the places where Ruiz and Pavon collected, I hope I shall be able 
& copy of it for an early number of the Botanical Miscellany. 
