REPORT ON OCEANIC CIRCULATION. 
35 
together with the extraordinarily high temperatures accompanying them, evidence the 
volume and dej^th of the powerful current from the Atlantic on which they depend. 
At 200 fathoms this ocean is still in free contact with the Atlantic, and the higher 
temperatures are well inshore. The highest isothermal is 43° to the south of the 
Lofoten Isles, and it is remarkable that the isothermals of 35° and 30° are much in the 
same positions as at thn 100 fathoms depth. The specific gravities are virtually 
identical with those at 100 fathoms, and at both depths they are highest midway between 
Norway and Spitzbergen. 
Except the comparatively narrow channel of the Wyville Thomson Ridge, the 
whole of this ocean at 300 fathoms is cut off from the Atlantic and becomes a “ closed 
sea,” and as a consequence the temperature now assumes a wholly different mode of 
distribution. The isothermals, instead of having a S.W. and N.E. course on the lines of 
the great ocean current, indicate an area of higher temperature, with its axis approximately 
about lat. 70° N., extending nearly as far west as Jan Mayen, but between it and the 
Faroe Ridge there is a much lower temperature^ 32°. Since in this cold area Mohn noted a 
specific gravity of 1'0262, the low temperature cannot be ascribed to upwelling, but its 
origin is rather to be referred to the north-west in the region marked out by the 
isothermal of 30°. The increase from 30° to 32° is derived from the upper denser 
waters, which, having passed the Faroe Ridge, have in their northerly course partially 
sunk to lower depths, and have consequently to some extent raised both the temperature 
and specific gravity. 
The warmer area to the north-east, marked by the isothermals of 39°, 37° and 35°, 
is coincident with the region where the great south-westerly current comes to a stop 
and the north-easterly current begins its course. A head of water is no doubt formed 
in the region where these south-westerly winds and attendant currents cease. The 
additional pressure thereby produced, and the high specific gravities, result in a 
downward movement of the upper waters, and consequently the raising of the 
temperature over the region where it occurs. The increase of temperature from this 
strong downward movement is less and less as the depth increases, but it is distinctly 
traceable at least as far as 700 fathoms, and is still accompanied with the high specific 
(gravities of the surface. 
The positions of the isothermals from 300 to 700 fathoms make it plain that the 
movements of the ocean at these depths are strongly downwards rather than 
horizontal ; that the influence of prevailing winds on the surface and deeper currents 
arising from them is no longer felt in any recognisable degree ; and that all movements 
are virtually restricted to those caused by difierences of temperature and salinity. The 
position retained by the region of higher temperature quite disproves the idea of the 
existence of any vorticose movement in these deep waters. 
At 1000 fathoms and greater depths the temperature to the south-west of Spitz- 
