34 
THE VOYAGE OF H.M.S. CHALLENGER. 
The Arctic Ocean (inclusive of the Norwegian Sea). 
This ocean is bounded on the south by the Faroe Ridge, at a depth not exceeding 
260 fathoms, extending from Iceland in a south-east direction to a point 45 miles south 
of Faroe. To this succeeds a deeper channel, the Wyville Thomson Ridge, 30 miles 
across, descending to 380 fathoms, on the east of which commences a shorter ridge, 
with a depth of 260 fathoms, connecting it with the mainland of Scotland. Since the 
shallowest part of the sea from Iceland to Greenland is less than 260 fathoms, it 
follows that this ocean is a “ closed sea ” at all depths greater than 260 fathoms, except 
for the short distance of 30 miles where the ridge sinks down to 380 fathoms. 
Owing to the prevailing south-westerly winds and accompanying current, the 
isothermals of the surface of the sea from 60° to 45° are pushed to higher latitudes than 
anywhere else on the globe, and it is to be remarked that the isothermals of the 
surface water of the sea are, for the same positions, much higher than those for the air. 
The line of maximum temperature is not close to the coast, but lies out in the Atlantic 
a considerable way from the west coasts of Europe. The extension of the isothermal 
of 40° eastwards round the north of Norway, and of the isothermal of 30° northwards 
beyond Spitzbergen, are points of great interest in connection with the distribution of 
the isobars and prevailing winds of this region. 
It is not only higher temperatures but also higher specific gravities that this great 
oceanic current conveys into high latitudes. Thus in the North Pacific the specific- 
gravity of 1-0260 extends only to about lat. 33° N., and in the South Pacific, South 
Atlantic, and Indian Ocean it just passes lat. 40° S. in a few places. In the North 
Atlantic, however, it extends as far north as lat. 72° N. and the specific gravity of 
1-0255 to lat. 78° N. This northern extension of the region of high temperature and 
specific gravity is doubtless occasioned by the complete absence of icebergs in the 
eastern division of this ocean. The important result is that the higher temperature of 
the surface descends to greater depths in this ocean than would otherwise be the case. 
The lowering of the specific gravities, by the rivers and rainfall, from the English 
Channel northwards along the west coast of Norway to Yardo is strongly marked. 
It will be observed that at 100 fathoms there is an area to the south-west of 
Spitzbergen, extending as the depth increases, where the temperature is only 30°. This 
is the region where the prevailing winds, after curving round from the south-west to 
the north-east, sweep along the fields of Arctic ice, in relation to which the course of 
the isothermal of 35° is interesting. At this depth the highest temperature is close in 
shore to the eastward. 
The specific gravities closely follow those of the surface. The mean of ten 
observations about lat. 73° N. and long. 0° to 40° E. is 1’0258, which is very greatly in 
excess of any specific gravity observed in any ocean in similar latitudes. These, 
