Page:The Botany of the Antarctic Voyage.djvu/542

506 Again, some of the Antarctic species have been detected floating in the atmosphere which overhangs the wide ocean between Africa and America. The knowledge of this marvellous fact we owe to Mr. Darwin, who, when he was at sea near the Cape de Verd Islands, collected an impalpable powder which fell on Captain Fitzroy's ships. He transmitted this dust to Ehrenberg, who ascertained it to consist of the siliceous coats, chiefly of American Dialomace&aelig;, which were being wafted through the upper regions of the air, when some meteorological phenomenon 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 scori&aelig; 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 78th degree of south latitude, and abreast of the Diatomace&aelig; 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 this 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 Diatomace&aelig;. In the Gulf of Erebus and Terror, 15 degrees north of Victoria Land, and placed in the opposite side of the globe, the soundings were of a similar nature with those of Victoria Land and Barrier, and the sea and ice as full of Diatomace&aelig;. 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 following systematically arranged catalogue of the hitherto described Antarctic species is drawn up from various papers by Professor Ehrenberg, but principally from that which appeared in the 'Monatsberichten der Berliner Akad. der Wissenschaften" for May, 1841, and which has been reprinted in Taylor's 'Annals of Natural History', and in the Appendix of Sir James Ross' 'Narrative of the Antarctic Expedition'. A few Falkland Island and Kerguelen's Land species have subsequently been examined by Mr. Thwaites, to whom, and to the Rev. Mr. Berkeley, I am much indebted for the assistance they have afforded me in this group. The arrangement of the genera followed is that of M. K&uuml;tzing's great work on this order.

1. EUNOTIA, Ehrb. 1. gibberula, Ehrb. Epithemia gibberula, ''K&uuml;tz. Kieselsck. Bacill''. p. 35. t. 29. f. 54, c.

Open Ocean, in Pancake-ice, Lat. 75&deg; S. Long. 170&deg; W.

An inhabitant of the Baltic Sea. Found fossil at Newhaven, in Connecticut, in volcanic ashes from the Rhine and amongst an atmospheric dust which fell near the Cape de Verd Islands.

2. amphioxys, Ehrb. K&uuml;tz. 1. c. p. 44. t. 30. f. 1.

Hab. Falkland Islands, Lesson. Cockburn Island, amongst the guano of a Penguin rookery.