474 



APPENDIX 



Note 18 (p. 60). 



The differentiation of the Main and South Equatorial Currents in 



mid- Atlantic. 



I will here deal with the indications that in mid- Atlantic the Main 

 Equatorial and South Equatorial Currents can be differentiated, 

 and that they are separate but contiguous currents. They are 

 afforded by six bottles that were dropped into the sea at different 

 times in the vicinity of the island of Ascension, the data for which, 

 supplied in five cases by Schott and in one case from the Nautical 

 Magazine, are given in the table below. They were cast over in 

 three cases on the north side of Ascension and in the other three 

 on the south side at distances varying between 50 and 350 miles 

 from the island. The southernmost, thrown over in 11° 38' S. 

 lat., was stranded on the coast of North Brazil (2° 40' S. lat.) ; the 

 others being recovered in three cases on Trinidad, one on the Grena- 

 dines, and one on the south-east coast of Jamaica. All these bottles, 

 even the southernmost, were borne along in the Main Equatorial 

 Current, none of them being carried south of Cape St. Roque. The 

 first three were solitary bottles that were thrown over in different 

 months and different years. The last three were thrown over on 

 three successive days from a ship proceeding north-west on the 

 track between St. Helena and Ascension, and they require particular 

 attention in this connection. 



The first thrown over about half-way between the two islands in 

 lat, 11° 38' S. was stranded at Paranahiba on the north coast of 

 Brazil in lat. 2° 40' S. The second starting from a position nearer 

 Ascension in lat. 10° 4' S., reached the Grenadines in the Lesser 

 Antilles in lat. 12° 42' N. The third cast over in lat. 8° 39' S. and 

 about fifty miles south-east of Ascension was recovered near Morant 

 Bay on the south-east coast of Jamaica in lat. 17° 56' N. The 

 implication is that bottles thrown over in the Main Equatorial 

 Current in the vicinity of Ascension reach the West Indies; whilst 

 those thrown into the same current half-way between St. Helena 

 and Ascension reach the coast of Brazil north of Cape St. Roque, 

 which divides the Main and South Equatorial Currents. From this 

 we should expect that if from the same ship bottles had been cast 

 over near St. Helena they would have been carried south when 

 approaching Cape St. Roque in the southern current. From this 

 point of view Ascension would be regarded as within the zone of 

 the Main Equatorial Current and St. Helena as in the track of the 

 South Equatorial Current. 



This is what was meant by the differentiation of these two equatorial 

 currents in mid-Atlantic, the drift of the main stream ultimately 

 getting into the Guiana Current and that of the southern stream 

 into the Brazilian Current. This distinction acquires importance 

 when we come to consider the current connections of Ascension and 

 St. Helena. From this standpoint they would be quite isolated 

 as far as direct communication by currents is concerned. Such 

 a view is supported by data supplied by a bottle which after being 



