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GEOLOGY OF NEW YORK CITY
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lands,
utterly unaccountable, except by the assumption of transportation, but
they are also discovered capping the cliffs of mountain chains, hanging
by the side of depths over which they must have been carried and into
which, by the Nemesis of destiny, they are now doomed to fall.
The
Jura Mountains, north of the great valley of Switzerland, and opposite
the western or Bermuda Alps, along the frontier of France, are thus
studded with these boulders, some of them containing 50,000 to 60,000
cubic feet of stone. These have come from the Alps; they are
crystalline rocks, gneiss and granite, and they lie upon ridges of
limestone. They are virtually nothing less than dislocated fragments of
those abraded and decreasing hills perched upon the Jura cliffs.
Professor Guyot has placed beyond all doubt their home upon the summit
and sides of the Swiss Alps, and shown that they have attained their
present eminence by a positive carriage from these original localities.
This position has, indeed, been made impregnable by a protracted and
laborious survey of innumerable " wanderers," found upon the Jura,
whose litho-logical character identified them with the Alpine
formation, while it served to trace the probable path of their
transmission. These blocks have been found at elevations ranging frorh
2,000 to 3,000 feet above the sea, and in Carinthia similar " erratics"
have been described at great elevations, proceeding from an opposite
quarter of the Alps.
In
North America, and especially throughout the Northern States, the
boulders are numerous, often of great size, and indicating transits of
many miles. Over the Eastern, Middle, and Northwestern States,
boulders, that have emigrated from distant points to the northward,
occur in such abundance that they may almost anywhere be found if the
inquirer will only examine the country he passes over. Upon Mount
Katahdin, in the Moosehead region of Maine, stones can be seen lying
over 4,000 feet above the sea, fossiliferous in their nature and coming
from northern sites; while, toward Mount Desert, masses some forty to
fifty feet in height are sprinkled every-
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