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RIDGE OF THE ANDES. oo 
except near the edge of the crater, which is sur- 
rounded by a small circular wall. In ascending it 
is extremely difficult to reach the lower bound- 
ary of the snows, the cone being surrounded by 
deep ravines ; and, after a near examination of the 
summit, Humboldt thinks he may assert that it 
would be altogether impossible to reach the brink 
of the crater. 
It was mentioned that, in the kingdom of New 
Grenada, the cordilleras of the Andes form three 
chains, in the great longitudinal valleys of which 
flow two large rivers. To the south of Popayan, 
on the table-land of Los Pastos, these three chains 
unite into a single group, which stretches far be- 
yond the equator. This group, in the kingdom of 
Quito, presents an extraordinary appearance from 
the river of Chota, the most elevated summits being 
arranged in two lines, forming as it were a double 
ridge to the cordilleras. These summits served for 
signals to the French academicians when employed in 
the measurement of an equinoctial degree. Bouguer 
considered them as two chains, separated by a lon- 
gitudinal valley; but this valley Humboldt views 
as the ridge of the Andes itself. It is an elevated 
plain, from 8858 to 9515 feet above the level of 
the sea; and the volcanic summits of Pichincha, 
Cayambo, Cotopaxi, and other celebrated peaks, are, 
he thinks, so many protuberances of the great mass 
of the Andes. In consequence of the elevation of 
the territory of Quito, these mountains do not seem 
so high as many of much inferior altitude rising 
from a lower basis. 
On Chimborazo the line marking the inferior li- 
mit of perpetual snow is at a height somewhat ex- 
