292 Royal Society : — On the Nature of the 



the North of Scotland and the Faroe Islands. It will be recol- 

 lei.'ted by those who have read my ' Lightning ' and ' Porcupine ' 

 ll.'ports on the exploration of this region, that whilst the whole 

 upper stnituni, from the surface to a depth of from 100 to loO 

 fathoms, has the temperature of the warm flow coming up from 

 tlie S.W., and whilst this temperature falls so gradually in the 

 " warm area " with increase of depth as to be still as high as 43° 

 Fahr. at a depth of (JOO fathoms, it falls so suddenly in the 

 "cold area" between 150 and 300 fathoms, that the whole of its 

 deeper stratum has a temperature below '62°, the bottom tempera- 

 ture descending in some parts to 2'J°'5. Now on this " cold area " 

 I never found a single Ololn>/erina, the bottom consisting of sand 

 and gravel, and the Foraminifera brought up from it being almost 

 exclusively those which form arenaceous tests. The "warm area," 

 on the other hand, is co\ ered with Globirjenna-ooza to an unknown 

 depth, its surface-stratum being composed of perfect shells filled 

 \y\\)\ sareode, whilst its deeper layers are amorphous. Near the 

 junction of the two areas, but still within the thermal limit of 

 the " warm," sand and Glohigerina-oozQ are mingled — this being 

 peculiarly noticeable on the '■'■ Iloltenia-groxxwik" which yielded a 

 large proportion of our most noteworthy captures in this locality. 

 Now, if the bottom-deposit is dependent on the life of the surface- 

 stratum, why should there be this complete absence of Glohiyerina- 

 ooze over the " cold area," the condition of the surface-stratum 

 being everywhere the same ? I was myself formerly disposed to 

 attribute it to the depression of bottom-temperature ; but as it has 

 now been proved by the ' Challenger ' observations in the Atlantic 

 that Globi(jerina-oozQ prevails over, areas whose bottom-tempera- 

 ture is but little above 32°, this explanation can no longer be 

 accepted. And I can see no other way of accounting for it than 

 by attributing it to the drift of the cold underflow, caryiug away 

 the Glohif/ennce that are subsiding through it towards the deep basin 

 of the Atlantic, into which I bebeve that underflow to discharge 

 itself. Prof. WyA'ille Thomson, however, denies any sensible 

 movement to this underflow, continuing to speak of it as " banked 

 up" by the Gulf-stream*, which here (according to him) has a 

 depth of 700 fathoms ; and this very striking example of want of 

 conformity between the surface-fauna and the bottom-deposit 

 consequently remains to be accounted for on his hypothesis. 



The other of Prof. Wyville Thomson's principal conclusions, as 

 to which I have rather a suggestion to offer than an objection 

 to take, relates to the origin of the " red clay " which he found 



* See his ' Depths of the Sea,' p. 400. That there is a lateral pressure of 

 the one flow against tlie other, just as there is a lateral pressure of the 

 Labrador Current against tlie Gulf-stream on the North-Ajnerican coast (pro- 

 ducing the well-known "cold wall "), is suflicieutly obvious from their relative 

 distritjution on the bottom of the channel. But it seems to nie perfectly clear 

 that the effect of this pressure is simply to narrow tlie glacial flow, and at the 

 same time to increase its velocity. The most westerly point to whidi wo tniced 

 it was near the edge of the Faroe Banks ; and tliere (as Prof. Wyville Thomson 

 himself pointed out to me at the time) the movement of the bottom-water waa 



