APPENDIX 



443 



days, the estimate employed in my table being 118 days. It may 

 be remarked that Laughton gives the average velocity of the current 

 as twenty to thirty miles a day {Physical Geography, 1873, p. 187). 

 A considerably shorter time would be occupied by the current in 

 carrying a bottle from the Gulf of Guinea (Anno Bom Island) to the 

 coast of Brazil (Cape St. Roque), a passage of about 2500 miles. At 

 the average rate of thirty miles a day it would require twelve weeks, 

 which is the estimate accepted in this work. 



We will proceed now with the discussion of the bottle-drift materials 

 employed in this treatment of the Main Equatorial Current. The 

 data may be arranged in the following groups : (a) those supplied 

 by the bottles thrown into the sea in the vicinity of Ascension, which 

 lies within the current but near its southern border; (b) those data 

 concerning bottles thrown into the northern portion of the current 

 in the vicinity of St. Paul's Rocks ; (c) those of bottles thrown into 

 the centre of the stream between St. Paul's Rocks and Cape St. 

 Roque ; (d and e) those of bottles thrown overboard off the Amazon 

 estuary. 



(a) The Ascension Area. — Probably the slackest portion of the 

 current is near its southern border in the vicinity of Ascension. 

 In the case of three bottles thrown overboard on successive days 

 in February from a ship on the course between St. Helena and 

 Ascension the following minimum daily rates are supplied by Schott 

 (pp. 14, 27; Maps I. and IV.) :— 



(1) 11-3 miles from a position half-way between these two islands 



to Paranahiba on the coast of North Brazil. 



(2) 11-7 miles from about 200 miles south-east of Ascension to 



the Lesser Antilles (Grenadines). 



(3) 18-1 miles from a position fifty or sixty miles south-east of 



Ascension to Jamaica (Morant Bay). 



Since the swiftest rate is afforded by the bottle that made by far 

 the longest passage (4017 miles), it is fair to conclude that there 

 was not the delay in its recovery that there was in the other two cases, 

 and probably nineteen or twenty miles a day would represent the 

 speed of its passage to the West Indies. It may be added that a 

 bottle dropped into the sea about 100 miles north-west of Ascension 

 in January 1822, which was picked up on Trinidad, gives a minimum 

 daily drifting rate of 15-6 miles (No. 45, Nautical Magazine, 1852). 



(b) The St. PauVs Rocks Area. — Just as Ascension lies a little 

 within the southern border of the current, so St. Paul's Rocks lie 

 just within its northern border. There are, in the first place, at my 

 disposal data for thirteen bottles dropped over in mid-Atlantic 

 between the meridians of 22° and 32° W. and the parallels of 5° N. 

 and 2° S., most of the materials being supplied by the American 

 charts. Of these, nine were stranded on the West Indian islands 

 between Trinidad and Martinique (inclusive), giving rates during 

 passages of from 1900 to 2400 miles of 20, 19-8 17-2, 16, 16, and 14-4 

 miles a day in the six most rapid cases. The two greatest velocities 

 apply to bottles that were thrown over in March and November, 



