Geographical Collections. 365 
To the east and north-west of the town of Arequipa, occurs the valley of the 
same name, surrounded by mountains covered with eternal snow. ‘The central 
peak of this group of nevadas, is the celebrated volcano of Arequipa. Its form 
and gigantic proportions allow of its being compared with the Cotapaxi of the 
Andes of Quito. Its elevation exceeds 18,000 feet. 
More to the south, between the parallels of Arica and of the Rio de Loa, are 
several volcanic cones of a great height. The most elevated, namely, the neva- 
das of Gualatieri and of Sahuma or Sehama, do not appear to be inferior to the 
Cerro of Chuquibamba. ‘The volcano of Gualatieri, in the Bolivian province of 
Carangas, rises above a table land of red sandstone, which contains much copper. 
The cone, which attains the region of eternal snow, offers the most imposing as- 
pect by its regular, almost geometric, form. There is not perhaps any moun- 
tain which can be compared to it, in this respect, in the whole chain of the 
Peruvian Andes. It is truncated, and allows the presumption that at its sum- 
mit there is a vast and deep crater. Vapour and smoke are constantly issuing 
from it; and, according to the report of the Indians who inhabit the village of 
Turco, at the foot of the mountain, flames also sometintes escape. 
The Sahuma presents two conical summits, which have the same regularity as 
that of Gualatieri. They are also formed of trachyte and trachytic conglomerates. 
Between the parallel of Sahuma and that of Tacora, (17° 51’,) there are seve- 
ral other volcanic mountains, some of which attain a height of 20,000 feet. The 
village of Tacora is the most elevated group of habitations upon the earth, 
(2232.2 toises..) It is situated in a little valley which separates two of these 
enormous volcanic cones. 
To the north-west of Tacora occurs the Nevada of Chipicani, upon the sum- 
mit of which a crater has burst open on the eastern side. A little farther a less 
elevated mainland offers the remains of an extinguished volcano, a true solfa- 
tara, whose vapours are condensed in the Rio Azufrado. The waters of this 
river, or rather of this torrent, are strongly impregnated with iron and sulphate of 
alum. They may be seen pouring from the solfatara itself, and in their rapid 
course towards the sea, they even attack animal organization, as in the Rio-Vi- 
nagre near Papayan. 
III. General Remarks.—A geognostic fact alluded to by Mr. Pentland as 
remarkable, is, that in no part of the volcanic regions of the chain of the 
Andes which he has crossed, has he found traces either of basalt or of py- 
roxene. Trachytic conglomerates, and trachytes mixed with grains of quartz, 
are the forms under which masses of volcanic origin present themselves most fre- 
quently. The trachytic pitchstones, obsidians, and other vitritied products of 
volcanoes, are extremely rare. 
Mr. Pentland mentions as a characteristic feature of the physical constitution 
of the ancient inhabitants ef Southern America, their inclination to elevate them- 
selves upon the highest parts of the chain of the Andes, and the faculty which 
they had of executing mining labours in those regions. The Cerro de Descuel- 
ga, situated upon the northern slope of the Illimani, is composed of transition 
slates, in which an immense quantity of veins, and of transported auriferous 
quartz, is met with; the north-western part is cut off almost vertically : it is 
nevertheless covered with little excavations, from whence the Peruvians obtained 
a great quantity of auriferous earth long before the conquest’ of the Spaniards. 
Several of these artificial excavations (bocas minas ) are met with at a height of 
16,600 feet. In other parts of High Peru, strangers are equally struck with the 
astonishing elevation at which mining excavations were carried on. All the 
Cerro de Potosi is at 16,0890 feet of elevation, and yet that mountain is covered 
up to its summit with wells and galleries. The entry of the gallery of San Mi- 
guel and of Pomaré, in the Peruvian province of Lampa, is still more elevated. 
It is close to the inferior limit of perpetual snows. 
The highest habitations of men, between the 14th and the 18th degree of 
south latitude, are more than 15,5090 feet in elevation, and little villages and post. 
