Geology. ; 409 
placed on the western slope of Rucu-Pichincha, differing from the other 
craters of the Ecuador, which takes the form at the summit of a regular 
cone covered with snow, it presents the figure of a truncated cone placed 
upon its inferior base, which is 1476 feet in diameter, and rises in height 
to 2296 feet. Its depth from the eastern side is enormous; and gazin 
upon the immense towers of dolerite and trachyte easiaie "2460 feet, 
sometimes vertically, sometimes in slopes more or less steep and varied, 
an impression is received which can never be effaced. Towards the west- 
ern part, the height of the walls of the crater diminishes gradually, leay- 
ing open to the east a fissure from whence the united waters escape 
during the rains or thaws. 
In the middle of the inclined plain which constitutes the bottom of the 
volcano, the actual cone of eruption rises; it is 820 feet in diameter, 262 
in height above the bottom of the middle of the crater, and 13,707 above 
the level of the sea, standing 4166 feet above Quito. This little moun- 
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fuerease - — A great ay of this mountain is covered wi 
vegetation; two regions, parting in opposite aw eet are ar it, 
‘two points from whence the cone of eruption . pie ee (one to the 
_ Centre, the other to he S.E.) there is given out in abundance a hot and 
table were which the crater sstoaver In order to examine its actual 
state, and to fill this blank, I descended on the 16th of last December, 
carrying, as far as possible, Ber was necessary for the perilous situa- 
tions in which I expected to be placed. I was ee oe little more than 
soca He 
the cone of aru The form which this presents, proves tha t the 
inclosure, interrupting it perpendicularly with a broad wall of 
Sudoubtediy y abth oat fom: its interior. Near to this, and towards the 
RCl 
a activity of Pichincha has increased remarkably, as is 
manifested by the greater exhalation of vapors. In 1845, the chimneys 
from whence the gases arose formed six groups, of which only one was 
considerable. oe sas col vapors escape by innumerable i nterstices and 
hollows, which the stones leave in each of the craters; and in the princi- 
‘SECOND SERIES, Vor. XXVI, No. 78.—NOV., 1958. 
53 
