96 On Similarities in the 



line, having water of under 1-022 density. South of the^ Congo 

 and as far as Loanda the surface density rises above 1-026 

 and is oceanic and free from river influences. 



On this line of section the part south of S. Thome is occupied 

 by ocean water, with river water superposed in places ; the part 

 north of the islands has a layer of intermediate Guinea current 

 water interposed between the underlying ocean water and 

 the overlying Niger water. Along this line the dependence 

 of the temperature of the subsurface layers on the distribution 

 of salinity in the water was evident. North of the island 

 of S. Thome we have large areas of river water on the surface 

 with comparatively fresh Guinea current water below. South 

 of that island the supply of river water is probably quite 

 as large, but it lies on the ocean water of temperate tropical 

 regions with a high surface salinity. While, therefore, we 

 find the actual surface temperature higher to the northward 

 of S. Thome, the subsurface water is warmer to the southward 

 of it. North of S. Thome, a temperature of 65 F. is found 

 at an average depth of about 35 fathoms ; south of that island 

 it is found as deep as 60 fathoms at a station where the density 

 (at 60 F.) of the water from the surface downwards was over 

 1-026. After passing the mouth of the Congo, equatorial features 

 disappear, and at a station near St Paul de Loanda, the cold 

 deep water was found approaching the surface, a temperature of 

 65 F. being found at 15 fathoms. Here we find the beginning 

 of the cold water of the windward shore of the South Atlantic. 



Diagram B is a meridional section on long. 14 W. down to 

 a depth of 200 fathoms, compiled from observations on board 

 the "Buccaneer" in March 1886, and the "Challenger" in 

 April 1876. The range is from 11 N. to 12 S. From 9 N. 

 to 11 S. the temperature of the surface is above 80 F., and 

 the isothermal of 80 travels at depths varying from 10 to 

 25 fathoms. From 10 N. to 4 S. the isotherm of 70 maintains 

 a nearly constant level of 25 to 30 fathoms ; to the southward 

 of 4 S. it dips deeper. The isotherm of 65 follows a nearly 

 parallel course. That of 60 comes within 30 fathoms of 

 surface at 4 S., and dips rapidly towards the south, more 

 gently towards the north. 



