48 FLOATING SEAWEEDS. 



without thunder. To the north of the Cape Verd 

 Islands they met with large patches of floating sea- 

 weed (Fucus natans), which grows on submarine 

 rocks, from the equator to forty degrees of latitude 

 on either side. These scattered plants, however, 

 must not be confounded with the vast beds, said 

 by Columbus to resemble extensive meadows, and 

 which inspired with terror the crew of the Santa 

 Maria. From a comparison of numerous journals, 

 it appears that there are two such fields of seaweed 

 in the Atlantic. The largest occurs a little to the 

 west of the meridian of Fayal, one of the Azores, 

 between 25 and 36 of latitude. The temperature 

 of the ocean there is between 60'8 and 68 ; and 

 the north-west winds, which blow sometimes with 

 impetuosity, drive floating islands of those weeds 

 into low latitudes, as far as the parallels of 24 and 

 even 20. Vessels returning to Europe from Monte 

 Video, or the Cape of Good Hope, pass through this 

 marine meadow, which the Spanish pilots consider 

 as lying half-way between the West Indies and the 

 Canaries. The other section is not so well known, 

 and occupies a smaller space between lat. 22 and 

 26 of N., two hundred and seventy-six miles east- 

 ward of the Bahama Islands. 



Although a species of seaweed, the Laminaria py- 

 rifera of Lanlouroux, has been observed with stems 

 850 feet in length, and although the growth of the^se 

 plants is exceedingly rapid, it is yet certain that in 

 those seas the fuci are not fixed to the bottom, but 

 float in detached parcels at the surface. In this 

 state, vegetation, it is obvious, cannot continue longer 

 than in the branch of a tree separated from the 

 trunk ; and it may therefore be supposed, that float- 

 ing masses of these weeds occurring for ages in the 

 same position, owe their origin to submarine rocks, 

 which continually supply what has been carried off 

 by the equinoctial currents. But the causes by 

 which these plants are detached are not yet suffi- 



