An account of the Fine Dust which often falls on Vessels in the Atlantic Ocean.

Abstract

Many scattered accounts have appeared concerning the dust which has fallen in considerable quantities on vessels on the African side of the Atlantic Ocean. It has appeared to me desirable to collect these accounts, more especially since Professor Ehrenberg's remarkable discovery that the dust consists in considerable part of Infusoria and Phytolitharia. I have found fifteen distinct statements of dust having fallen; and several of these refer to a period of more than one day, and some to a considerably longer time. Other less distinct accounts have also appeared. At the end of this paper I will give the particular cases, and will here only refer to the more striking ones and make a few general remarks. The phænomenon has been most frequently observed in the neighbourhood of the Cape Verd Archipelago. The mnost southern point at which dust is recorded to have fallen is noticed by Capt. Hayward, on whose vessel is fell whislt sailing from lat. 10° N. to 2° 56′ N.; the distance from the nearest of the Cape Verd Islands being between 450 and 850 miles. respecting the northern limit, the water fro the great distance on both sides of C. Noon (in lat. 28° 45′) is discoloured owing in part, according to Lieut. Arlett, to the quantities of falling dust. Hence the phænomenon has been observed over a space of at least 1600 miles of latitude. This dust has several times fallen on vessels when between 300 and 600 miles from the coast of Africa