From Madeira to Tristan d'Acunha. yy 



speak more definitely, the warm surface-water at the equator 

 is replaced by water flowing in from the colder strata im- 

 mediately adjoining, which must result in the formation and 

 maintenance of a stratum of cold water immediately below the 

 surface of the equatorial belt. This cold stratum, in the present 

 case, is found to extend to a depth of about 400 fathoms. 



In this sense the cold water may be said to rise up towards 

 the surface at the equator, but if we compare the thickness of 

 the strata under consideration with their horizontal extension in 

 latitude and longitude, whatever movement may take place in a 

 vertical direction must be absolutely insignificant in comparison 

 with the horizontal currents thus created. This inflow of cold 

 water will take place more or less along the whole boundary 

 between the equatorial belt and the colder belt immediately 

 adjoining, and this agrees with the extension of the cold stratum 

 along the whole section between Cape Palmas and Cape 

 S. Roque, the current being stronger in the western half than 

 in the eastern. There are several indications of a large mass of 

 cold water moving across the equator and the plateau of St. Paul 

 Rocks in a north-easterly direction, and forming an under-current, 

 which may be traced as far as the Cape de Verde Islands 

 along the West Coast of Africa, and between the latter and the 

 Canaries, Madeira, and even the Josephine Bank, off the Straits 

 of Gibraltar. 



The abrupt gradient of the temperature-curve which is so 

 characteristic of the equatorial stations (Curve Fig. 9) is also 

 observed at Station 95, Station 96, and Station 97, and to a 

 slightly lesser extent at Stations 98, 99, and 100. In fact, this 

 form of curve makes its appearance immediately south of the 

 Cape de Verde Islands, and thence extends towards the equator. 

 The cold current, after crossing the equator in an oblique direc- 

 tion from S.W. to N.E., probably divides itself off the coast of 

 Africa into two branches, one flowing north, between the Cape 



