1876.] on board the ' Valorous^ in August 1875. 233 



it appears, from the temperature-souudings taken further north towards 

 Disco Island by the Swedish ship ' Ingegera' (Plate 3. Xos. I.-V.)? ^^'^^ 

 water as cold as this, and even much colder (31° being recorded in one 

 instance), is there found at depths varying between 58 and 185 fathoms ; 

 and it can scarcely be doubted that the water which is chilled by the more 

 severe cold of Baffin's Bay is here flowing down the slope of Davis 

 Strait. i\gain, it is at first sight an anomaly to find at Station YIII. a 

 bottom-temperature of 34°*6 at 1350 fathoms, while the bottom-tempe- 

 ratures both to the north and to the south of it are 31:"-6 ; but this only 

 shows that the coldest Polar water is flow ing south through some deeper 

 channel, perhaps in the western half of Davis Strait*. And the same 

 explanation applies to the yet more remarkable fact that a bottom-tem- 

 perature of 33°'4 was met with near the mouth of Davis Strait, when no 

 such water was met with further north. But that even this does 

 not carry down the coldest water of the Arctic basin, is ob^'ious from 

 the fact brought to light by the 'Porcupine' temperature-soundings 

 in the " Lightning Channel " (between the north of Scotland and the 

 Paroe Islands), over a large part of whose bottom we found the tempe- 

 rature to range two degrees, or even more, heloiu 32°. 



The next temperature-sounding (Plate 2. Station 11, Plate 4. ]S^o. XL), 

 taken on the 17th of August almost exactly in the meridian of Cape 

 Parewell, and not quite two degrees to the south of it, gave, like 

 No. IX., a bottom- temperature of 33°'4 at 1860 fathoms; so that it 

 seemed pretty clear that this is the temperature of the coldest water 

 that can find its way into the Xorth Atlantic along either the west or 

 the east coast of Greenland. And from the depth at which the isotherm 

 35° was found to lie in the 1660 fathoms serial sounding, it is obAious 

 that the stratum between 35° and 33°-4 must be here a A ery thin one ; 

 whilst the upward slope which is indicated by the next sounding sho^vs 

 that it must rapidly die out towards the east. 



The course of the ' Valorous ' having then been kept at first nearly due 

 East, and afterwards S.E., another serial temperature-sounding (Plate 2. 

 Station 12, Plate 4. No. XII.) was taken on the 19th of August in Lat. 

 56° 11' N., and Long. 37° 41' W. The surface-temperature had here 

 risen to 53°, — about the same as we had encountered in the "Light- 

 ning Channel," at the same time of the year, rather further to the 

 north ; bnt the warm upper stratum was here thinner, a reduction 



* As I pointed out on a former occasion (Proc. Eoy. Soc. vol. xx. p. 624. § 144), 

 any water moving from either Pole towards the Equator will have a zvesterly tendency 

 in virtue of its deficiency of easterly momentum ; just as water moving from the 

 Equator towards either pole will have an easterly set, in virtue of the excess of easterly 

 momentum which it carries with it. — The later temperature-soundings of the ' Chal- 

 lenger ' in the South Atlantic have given the explanation of the temperature of 32° -4 

 observed under the Equator in the first year of her voyage, but not encountered in any 

 of the earlier temperature-soundings taken in the South Atlantic, by showing that the 

 coldest Antarctic underflow is met with on the ivesterly part of its sea- bed. 



