834 HALL’S EXCURSIONS. 
cates with the city by a brick bridge, the height of which is 
— feet above the bottom of the dell. It is evident from 
their perpendicular sides that these fissures have not been 
gradually formed by descending waters: we must therefore 
consider them as rents, caused by the action of the volcano, 
at a period beyond the reach of tradition, probably ere it had 
worked itself the present outlet, on the opposite side of the 
mountain. The first part of our ascent lay through the 
cultivated lands of a farm, belonging to the convent. Not 
only Barley, but Maize and Potatoes, are grown to the height 
of near 12,000 feet. The average limit of cultivation may 
be placed, everywhere in the Andes, at betwixt 11,000 and 
12,000 feet, subject of course, to local variations. The 
farm of Licso, belonging to Antisana, round which have 
been observed considerable crops of Barley, is, by M. 
Boussingault’s barometrical measurement, 11,440 feet above 
the level of the sea. The farms at the foot of Chimborazo 
are equally elevated. The mean temperature of these 
heights (about 45°), would be insufficient to ripen the harvest, 
without the aid of the sun’s vertical rays, which supply the 
want of a continued summer-heat. After passing this zone 
of cultivation, we entered the more picturesque region of 
thickets and pastures, which extends from about 10,000 to 
13,000 feet. This central girdle, which is nearly uniform in all 
the Quitenian Andes, is principally composed of Barnadesia 
spinosa, Berberis glauca, Rubus glabratus, Hypericum laricifo- 
lium, Andromachia igniaria, Lobelia biserrata ? alow bushy tree, 
called by the Indians, from the figure of its leaf, Puma maqui, 
(Lion’s paw,) and a variety of syngenesious shrubs, among 
which is (5. No. 8.), distinguished for its fragrance, (20. No. 
8.) a Melastoma—? with scarlet calyx and paleyellow blossoms 
abounds from nearly the level of Quito; various species of 
Oxalis, Valeriana, Stellaria, Geum—? (14. No. 8,) and Viola ? 
flourish in the shade. The Fragosia aretoides, mixed with 
Eryngium, and a species of Alchemilla with an orbicular 
serrated leaf, forms a turf remarkable for its rigid density, on 
the whole of the ascent from Quito: two species of Andromeda, 
