RED FOG OF THE ATLANTIC. 13 



been seen almost all over the world, having made their first 

 appearance in England on the 9th of November. Here they 

 were noticed, more or less, for many weeks ; and from ob- 

 servations made at Berlin during the last three days of 

 November, it was calculated that the reflecting matter must 

 even then have been suspended at a height of forty miles 

 above the earth. 



But the dust which constitutes the chief part of the " red 

 fog " of the Atlantic, the " sea-dust " of the northern seas, 

 and the " sirocco-dust " of South Europe, is neither cosmic 

 nor volcanic, though it, too, has travelled great distances. 



Vessels, hundreds of miles from land, have been at times 

 enveloped for days in fog consisting of a brick-red or cin- 

 namon-coloured dust, which covered the sails and rigging 

 with a thick coat, and rendered the air so hazy that no 

 vessel which was more than a quarter of a mile off could be 

 distinguished even at mid-day. Off St. Jago, during certain 

 months of the year, a very fine dust is almost constantly 

 falling, which, says Mr. Darwin, roughens and slightly in- 

 jures astronomical instruments, hurts the eyes, dirties every- 

 thing on board, and at times falls so thickly that vessels 

 have been known to run ashore owing to the obscurity, and 

 are recommended to avoid the passage between Cape Verd 

 and the Archipelago. Considerable quantities continued to 

 fall upon the Beagle when she was between three and four 

 hundred miles from shore, some of the variously-coloured 

 transparent particles being a thousandth part of an inch 

 square, few larger, and the greater part consisting of fine 

 powder. On the succeeding days, as the vessel proceeded 

 on her way, the dust became so fine that it could be col- 



