1834.) ERRATIC BOULDERS. 247 
height. Some of the icebergs were loaded with blocks of no 
inconsiderable size, of granite and other rocks, different from the 
clay-slate of the surrounding mountains. The glacier furthest 
from the Pole, surveyed during the voyages of the Adventure 
and Beagle, is in lat. 46° 50’, in the Gulf of Penas. It is 15 
miles long, and in one part 7 broad, and descends to the sea- 
coast. But even a few miles northward of this glacier, in the 
Laguna de San Rafael, some Spanish missionaries * encountered 
‘“ many icebergs, some great, some small, and others middle- 
sized,” in a narrow arm of the sea, on the 22nd of the month 
corresponding with our June, and in a latitude corresponding 
with that of the Lake of Geneva! 
-In Europe, the most southern glacier which cpmes down to the 
sea is met with, according to Von Buch, on the coast of Norway, 
in lat. 67°. Now this is more than 20° of latitude, or 1230 
miles, nearer the pole than the Laguna de San Rafael. The 
position of the glaciers at this place and in the Gulf of Penas, 
may be put even ina more striking point of view, for they de- 
scend to the sea-coast, within '73° of latitude, or 450 miles, of a 
harbour, where three species of Oliva, a Voluta, and a Terebra, 
are the commonest shells, within less than 9° from where palms 
grow, within 43° of a region where the jaguar and puma range 
over the plains, less than 24° from arborescent grasses, and 
(looking to the westward in the same hemisphere) less than 2° 
from orchideous parasites, and within a single degree of tree- 
ferns! ; 
These facts are of high geological interest with respect to the 
climate of the northern hemisphere, at the period when boulders 
were transported. I will not here detail how simply the theory of 
icebergs being charged with fragments of rock, explains the origin 
and position of the gigantic boulders of eastern Tierra del Fuego, 
on the high plain of Santa Cruz, and on the island of Chiloe. - 
In Tierra del Fuego, the greater number of boulders lie on the 
lines of old sea-channels, now converted into dry valleys by the 
elevation of the land. They are associated with a great unstrati- 
fied formation of mud and sand, containing rounded and angular 
fragments of all sizes, which has originated} in the repeated 
* Agiieros, Desc. Hist. de Chiloe, p. 227. 
+ Geological Transactions, vol. vi. p. 415. 
