304 



PLANTS, SEEDS, AND CURRENTS 



later to the north-east monsoon they would have been carried to 

 the south-west, and might have been the sport of the currents for 

 years. This seems to have been the fate of a bottle cast over in 

 May in lat. 6° S. to the south-east of the Seychelles, which was 

 recovered two and a quarter years after in the Chagos Islands, 800 

 miles to the eastward (Schott, p. 21, Map 5, No. 8). So again the 

 bottle before mentioned which was found on the shores of Equatorial 

 Africa 160 days after it had been dropped into the sea in 2° N. lat., 

 some 400 miles west of Sumatra, began its passage in January, that 

 is, in the height of the north-east monsoon. Had it started in July 

 during the height of the south-west monsoon, it would have been 

 carried back to Northern Sumatra or the Malay Peninsula, as is 

 well brought out in Schott' s map in the case of other bottles. 



The general effect of the alternating influence of the surface drift 

 currents set up in the equatorial waters of the Indian Ocean by the 

 monsoons would be to restrict the arrival on the coasts of Equatorial 

 Africa of drift from Malaya and North-west Australia to the half 

 of the year corresponding to the period of the north-east monsoon. 

 In the other half of the year, if it did not become the sport of the 

 currents between Ceylon and Madagascar, it might be stranded 

 almost anywhere on the shores of the northern half of the Indian 

 Ocean. 



This leads us to consider the current- connections of the east side 

 of Africa with Western Australia, and in so doing we shall be compelled 

 to cover old ground. Here the South Equatorial Current, or the 

 South-east Trade Drift, is the direct transporting agency, and Africa 

 thus figures as the recipient. The track that seeds from the tropical 

 coasts of North-west Australia would take is indicated (a) by the 

 bottle, already alluded to, that after being dropped into the sea 

 about half-way between Sumbawa and the opposite Australian shores 

 passed close to Keeling Atoll and was stranded on the Chagos Islands, 

 (b) by the two bottles before mentioned that were carried from 

 Keeling Atoll to Brava on the African coast in 1° N. lat. Such 

 seed-drift would presumably, therefore, reach Equatorial Africa. 

 It would be derived from the adjacent coasts of North-west Australia 

 and Malaya and from the shores of the Arafura Sea. 



But drift from Western Australia in the vicinity of and to the 

 south of the North-west Cape would also come within the influence 

 of the South-east Trade Current. With the same northerly slant 

 that is exhibited in the track of the drift from the Timor and Arafura 

 Seas, it would arrive at a point in mid-ocean — about the 15th parallel 

 of south latitude and the 75th meridian of east longitude — where 

 it would have to choose between a course lying north of Madagascar 

 bringing it to the vicinity of Zanzibar, and a course south of Madagascar 

 bringing it into the Natal Current and resulting in most cases in its 

 being stranded on the shores of Cape Colony. The probable deter- 

 mining cause would lie in the indirect influence of the monsoons 

 some degrees further north, the northern course being taken during 

 the south-west monsoon and the southern course in the north-east 

 monsoon. 



The sequence of events is clearly shown in No. 5 of Schott's charts. 



