314 THE DEPTHS OF THE SEA. [CHAP, VIT. 
47, 90, 49, 50, and 51, is in the warm area. There 
is no great difference in depth between the two series 
of soundings; and there is no indication of a ridge 
separating them. The only possible explanation of 
these two so widely different submarine climates, 
existing apparently under the same circumstances 
and in close proximity to one another, is that the 
Arctic indraught which passes into the deeper part 
of the Féroe Channel is banked in at its entrance, 
by the warm southern stream slowly passing north- 
wards. There is a slight but very constant depres- 
sion of the isothermal lines of surface temperature 
in the shallow water along the west coast of Britain. 
This, I believe, indicates that a portion of the cold 
Féroe stream makes its escape, and, still banked in 
close to the land by the warm water, gradually makes 
its way southwards, so mixed and diluted as only to 
be perceptible by its slight effect on the lines of mean 
temperature. Diagrams 55 and 56 illustrate the dis- 
tribution of temperature in the cold and warm areas 
respectively ; and in Fig. 57, the results of the serial 
soundings Nos. 52, 64, and 87, are reduced to curves. 
From these diagrams, taken together, it will be seen 
that in the first 50 fathoms there is a rapid fall of 
nearly 3° C. Station No. 64 is a good deal farther 
north than the other two, and the surface tempera- 
ture is lower, so that the fall, which is nearly to the 
same amount, starts from a lower point. The surface 
temperature is doubtless due to the direct heat of 
the sun, and the first rapid fall is due to the rapid 
decrease of this direct effect. From 50 to 200 fathoms 
the temperature in all three cases falls but little, re- 
maining considerably above the normal temperature 
