40 THE "SARGASSO" SEA. 



way the Crosier Nautilus (Spirula Peronii) sometimes 

 reaches our coasts ; and the lanthina, or blue sea snail, 

 travelling by the same road, pays us its nearly regular 

 autumnal visit. In this way too, a large palm stem, 

 now in the Dublin University Herbarium, reached the 

 shores of Valentia in Kerry; and I have frequently 

 found West India seeds, and sometimes cowries, on the 

 coast of Clare. I have elsewhere noticed the many 

 southern sea-weeds which attain their greatest northing 

 on the Irish coast. 



To the gulf-stream, too, we must ascribe the origin 

 of the vast floating masses of sea-weed, first seen by 

 Columbus, and noticed by all subsequent mariners, in 

 the central region of the Atlantic. The " Sargasso" 

 sea occupies exactly the space between the currents 

 flowing east and west, or what we may call the dead 

 water in the centre of the Atlantic whirlpool. It is 

 reasonable to suppose that the floating weed has been 

 brought from time to time to this part of the sea, and 

 being thrown out of circulation by the revolving cur- 

 rent, and continuing to vegetate on the surface, has 

 gradually accumulated and increased. 



The direction of surface currents is frequently ascer- 

 tained by " track bottles;" that is, closed bottles thrown 

 overboard from ships, containing a note of the date and 

 place at which they were committed to the sea. These 

 float with the current until they are either picked up or 

 stranded, and the place and time at which they may 

 be found compared with the enclosed register, give the 

 general direction and force of the current. Such bottles 

 have been found to take thirteen months to reach 



