28 EDWARDS : 



perhaps ultimately depends for its existence. It maintains 

 that balance between the animal and vegetable kingdom 

 which prevails through all other latitudes ; probably also 

 purifying the vitiated atmosphere as plants of higher orders 

 do in most temperate regions. 



"III. The genera and species of Diatomacece collected 

 within the Antarctic Circle are not all peculiar to those latitudes; 

 on the contrary, some of the latter occur in every country 

 between vSpitzbergen and Victoria Land. Others, or even some 

 of these, have been recognized by Prof. Ehrenberg as occurring 

 fossil in both Americas, the south of Europe and the north of 

 Africa, in tripoli stone and volcanic ashes ejected by living 

 and extinct volcanoes ; whilst others again have been found 

 floating in the atmosphere which overhangs the tropical 

 Atlantic ; for Mr. Darwin during the vo3'age of the " Beagle " 

 collected an impalpable dust which fell on Captain Fitzroy's 

 ship when to the west of the Cape de Verde Islands, and which 

 on examination was proved to consist of the remains of Uia- 

 tomacea;, including species common to the Antarctic regions. 



"IV. The death and decomposition of the Antarctic 

 vegetation are gradually producing a submarine deposit or 

 bank of vast dimensions. This bank consists mainly of the 

 shields (the siliceous coatings of Diatomaceae) intermixed 

 with Infusoria and inorganic matter. Its position is from the 

 76th to the jStli degree of south latitude, and between the 

 meridians of 26.5 east and i6oth west longitude, thus occupy- 

 ing an area of 400 miles long by 120 wide. All the soundings 

 taken over this deposit were in the finest green mud, occas- 

 ionally mixed with sand, and a depth of between 200 and 400 

 fathoms. The lead sometimes sunk two feet into this peaty 

 deposit, and on examination of what it brought up, showed 

 the bottom to consist in a great measure of the remains of 

 the species living on the surface. 



" V. This deposit may be regarded as resting on the 

 shores of A'ictoria Land and Barrier, and hence on the sub- 

 marine flanks of Mount I{rebus, an active volcano upwards of 



