e wide ocean between Africa and America. The
knowledge of this marvellous fact we owe to Mr. Darwin, who, when he was
at sea off the Cape de Verd Islands, collected an impalpable powder which
fell on Captain Fitzroy's ship. He transmitted this dust to Ehrenberg,
who ascertained it to consist of the silicious coats, chiefly of American
_Diatomaceoe_, which were being wafted through the upper region of the
air, when some meteorological phenomena checked them in their course and
deposited them on the ship and surface of the ocean.

"The existence of the remains of many species of this order (and amongst
them some Antarctic ones) in the volcanic ashes, pumice, and scoriae of
active and extinct volcanoes (those of the Mediterranean Sea and
Ascension Island, for instance) is a fact bearing immediately upon the
present subject. Mount Erebus, a volcano 12,400 feet high, of the first
class in dimensions and energetic action, rises at once from the ocean in
the seventy-eighth degree of south latitude, and abreast of the
_Diatomaceoe_ bank, which reposes in part on its base. Hence it may not
appear preposterous to conclude that, as Vesuvius receives the waters of
the Mediterranean, with its fish, to eject them by its crater, so the
subterranean and subaqueous forces which maintain Mount Erebus in
activity may occasionally receive organic matter from the bank, and
disgorge it, together with those volcanic products, ashes and pumice.

"Along the shores of Graham's Land and the South Shetland Islands, we
have a parallel combination of igneous and aqueous action, accompanied
with an equally copious supply of _Diatomaceoe_. In the Gulf of Erebus
and Terror, fifteen degrees north of Victoria Land, and placed on the
opposite side of the globe, the soundings were of a similar nature with
those of the Victoria Land and Barrier, and the sea and ice as full of
_Diatomaceoe_. This was not only proved by the deep sea lead, but by the
examination of bergs which, once stranded, had floated off and become
reversed, exposing an accumulation of white friable mud frozen to their
bases, which abounded with these vegetable remains."

The _Challenger_ has explored the Antarctic seas in a region intermediate
between those examined by Sir James Ross's expedition; and the
observations made by Dr. Wyville Thomson and his colleagues in every
respect confirm those of Dr. Hooker:--

"On the 11th of February, lat. 60 deg. 52' S., long. 80 deg. 20' E., and Ma