462 



Messrs. Carpenter, Jeffreys, and Thomson [Nov. 18, 



presence of Volcanic detritus on that part of the floor of the channel between 

 the Faroe Islands and Iceland which lies between its deepest point and the 

 S.E. shore of Iceland has been already urged by Dr. "Wallich *, with great 

 force, as an argument for the existence of" an offshoot of the Arctic current 

 slowly moving downwards " in a line about 250 miles to the westward of 

 that which we consider ourselves to have now conclusively established ; and 

 it can scarcely be doubted that a set of Temperature-soundings taken in "the 

 682-fathom locality about forty miles from the southern shore of Iceland" 

 would give Thermometric results similar to those we have obtained in the 

 corresponding channel between the Faroe and Shetland Isles. — The import 

 of the presence of similar Volcanic detritus on the bed of the Mid-Atlantic, 

 as first pointed out by Prof. Bailey, will be considered hereafter (§ 1 1/). 



102. Although the thermal condition of the Warm area does not afford 

 the like striking evidence of the derivation of its whole body of water from a 

 Southern source, yet a careful examination of its phenomena seems fairly 

 to justify such an inference. For it has been shown by the Serial sounding 

 No. 87 in Lat. 59° 35', that while the surface-water is about 4|° warmer 

 than the water at 50 fathoms' depth, the latter is only 0 o, 8 warmer than 

 the water at 100 fathoms; and that below this the thermometer remains 

 almost stationary down to 400 fathoms. Now at that depth it is only 2°*4 

 colder than water at the same depth (Station 42) at the northern border 

 of the Bay of Biscay, in a Latitude more than 10° to the south, where the 

 surface-temperature was 62°*7 ; and the approximation of the two tempera- 

 tures is yet nearer at still greater depths, the bottom-temperature at 767 

 fathoms at Station 87 being 41°*4, whilst the temperature at 750 fathoms' 

 depth at Station 42 is 42 0, 5. So great an excess above the Isotherm 

 of Lat. 59° 35' can scarcely be attributed to the summer atmosphere of 

 the locality, which we scarcely ever observed to be above 54°, and of which 

 the effect, if exerted at all, seems limited to the "superheating" of the 

 superficial stratum. It is obvious, again, that the surface- drift caused by 

 the prevalence of South-westerly winds, to which some have attributed the 

 phenomena usually assigned to the extension of the Gulf-stream to these 

 regions, cannot account for such an elevation of temperature in a stratum 

 altogether removed from its agency ; and it seems equally difficult to 

 conceive that in a region so remote from the source of the Gulf-stream 

 proper, its influence, even if exerted in an elevation of the surface-tempe- 

 rature, should extend to a depth of at least 400 fathoms. It may be 

 pretty certainly affirmed, indeed, that the effect of the warm current is 

 exerted to the very bottom of the "Warm area : for its temperature even at 

 767 fathoms is 41°*4, which is several degrees above the theoretical iso- 

 therm of the latitude ; and such a temperature could scarcely be maintained 

 at this elevation against the depressing influence of the Polar current which 

 here mingles with it, were it not for a continual influx of warm water from 

 a Southern source. 



* North-Atlantic Sea-bed, pp. 5-7. 



