From Falkland Islands to Cape of Good Hope. 87 



isotherms of io° C. and of 2°.5 C. over the plateau of Tristan 

 d'Acunha and Gough Islands deserves notice. The depth of 

 the isotherms of io° C. and 5 C. in the eastern portion of this 

 section differs but little from that in the western portion. The 

 concave shape of these isotherms between Tristan d'Acunha and 

 the Cape is due probably to the influence of a comparatively 

 warm surface-stratum, which, however, soon comes in contact 

 with the cold bottom-stratum, for at Station 136, 4 C. was 

 registered at 400 fathoms; at Station 137, 2°.6 C. at 700 

 fathoms; at Station 138, 3°-3 C. at 500 fathoms ; and at Station 

 139, 3°. 1 C. at 400 fathoms. The high level of the isotherm 

 of 2 . 5 C, rising in this section to 600 fathoms from the surface, 

 while in the North Atlantic its position is generally at 1500 

 fathoms, proves the inflow of cold water from the Southern 

 Ocean into the Atlantic basin, and the gradual rise of the tem- 

 perature of the bottom strata as we proceed along the meridian 

 from South to North. 



