476 



APPENDIX 



drift that it has captured from the two equatorial currents. This 

 would be especially the case, as pointed out by Schott (p. 17), with 

 the drift of the southern current. But the important feature is 

 that the Guinea Current during the northern summer extends much 

 farther west than in winter. During a portion of the year this current 

 is restricted mainly to the eastern half of the Atlantic ; but it may 

 at other times extend to the vicinity of the South American and 

 West Indian region and assume the role of a true counter-equatorial 

 stream. The extension westward and the withdrawal eastward of 

 this current greatly affects the drifting direction of bottles thrown 

 overboard in the area above described. Schott carefully worked 

 out this point, and from his results, elaborated on page 17 of 

 his memoir, it appears that we have the real explanation why bottles 

 dropped into the sea in this area at the same place in different seasons 

 arrive in one case at the American and in another at the African side 

 of the ocean. 



Whilst the varying behaviour of the bottles as indicated by Schott 

 would limit the extension and retreat of the Guinea Current within 

 the meridians 22° and 32° W., the actual extension westward may 

 be much greater. We learn from the Admiralty publication (Africa 

 Pilot, Part I., 1907, p. 49), that its western limit can be traced at 

 all seasons of the year as far as the 23rd meridian (W. long.), but that 

 in the summer and autumn months an easterly current extends as 

 far west as the 53rd meridian. " This is probably " (as the writer 

 proceeds to remark) " an expansion of the Guinea Current proper, 

 or a counter-equatorial current." Laughton (p. 225) is representative 

 of those who treat the counter-equatorial current as a thing apart 

 from the Guinea current. It may be that the difference in view 

 is only concerned with a difference in names. The Admiralty view 

 that the first is a summer and autumn extension of the second is 

 directly stated in Captain Jackson's Winds and Currents (p. 26, 

 1904). 



It is in its character as a counter-equatorial stream that the Guinea 

 Current attracts the interest of the student of the trans-oceanic 

 distribution of seeds in this part of the Atlantic. We are wont to 

 consider that through the agencies of the two equatorial streams 

 Africa figures only as the giver and the West Indian and tropical 

 American region as the recipient in the process of distribution of 

 seeds by currents in these warm latitudes. But here we have pre- 

 sented the possibility of a reversal of the operation, when Africa 

 becomes the borrower from the New World. On account of the 

 great predominance of the westerly drift currents in these seas the 

 indications of the floating bottle would as a rule illustrate only 

 the transference of drift from the African to the American side of the 

 Atlantic. But occasionally the track of a bottle from the American 

 to the African side breaks through this routine. Thus in Schott's 

 first map there is the course laid down of a bottle (No. 425) which 

 was recovered on the coast of Sierra Leone after being cast overboard 

 in March about 270 miles N.E. of Cape St. Roque, and less than a 

 hundred miles north of the island of Fernando Noronha, the approxi- 

 mate position being in about 2° S. lat. and 32° W. long. Its track 



