in the Ocean at the South Pole. 
125 
3. Water from the equatorial ocean in the direction of St. Louis, 
in Brazil, in 0° lat., 28° W. long. 
A. SILICEOUS POLYGAS'l'RICA. 
1. Fraqilariu rhabdosoma. 2. Fragilaria Navicula. 
13. SILICEOUS PH YTOLITH ARIA. 
3. Lithostylidium rude. 4. Lithostylidium Serra. 
4. Water from the Antilles Ocean, 24° N. lat., 40° W. long. 
A. SILICEOUS POLYGASTRICA. 
1. Haliomma radiatum. 
B. SILICEOUS PH YTOLITH ARIA. 
2. Lithodontium nasutun. 4. Lithostylidium rude. 
3. Lithostylidium Amphiodom. 
C. MEMBRANOUS PORTIONS OF PLANTS. 
5. Pollen Pini. 
It follows from these four series of observations obtained 
through M. Schayer, that the ocean, in its usual condition, 
without peculiarity of colour, without storms and other in¬ 
fluences, contains, in the most transparent sea-water, numerous 
perfect and wholly invisible organisms suspended in it, and that 
the siliceous-shelled species are the most predominant in all those 
cases, although the analysis of sea-water does not show silica as 
a constant ingredient. 
III. On a Cloud of Dust which rendered the whole air hazy for a 
long time in the high Atlantic Ocean in 17° 43 / N. lat., 26° W. 
long., and its being constituledof numerous siliceous animalcules. 
Mr. Darwin, the well-known and most meritorious English 
traveller and writer on coral reefs, relates in the account of his 
travels, that a fine dust constantly fell from the hazy atmos¬ 
phere off the Cape Verd Islands, and also on the high sea of 
that region, while he was there; and likewise on a ship, which, 
according to the account in his letter, was 380 sea-miles distant 
from land. The wind was then blowing from the African coast. 
Mr. Darwin has sent to the author for examination a sample of 
