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 unstratified
formation of mud and sand, containing rounded and angular fragments
of all sizes, which has originated in the repeated ploughing up of
the sea-bottom by the stranding of icebergs, and by the matter
transported on them. (11/15. "Geological Transactions" volume 6
page 415.) Few geologists now doubt that those erratic boulders
which lie near lofty mountains have been pushed forward by the
glaciers themselves, and that those distant from mountains, and
embedded in subaqueous deposits, have been conveyed thither either
on icebergs, or frozen in coast-ice. The connection between the
transportal of boulders and the presence of ice in some form, is
strikingly shown by their geographical distribution over the earth.
In South America they are not found farther than 48 degrees of
latitude, measured from the southern pole; in North America it
appears that the limit of their transportal extends to 53 1/2
degrees from the northern pole; but in Europe to not more than 40
degrees of latitude, measured from the same point.
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