546 



Dr. W. B. Carpenter on the 



[June 13, 



the superficial layer, in which it is more than twice as great as it is 

 beneath. 



14. Now, that there is a slow N.E. movement of the upper stratum of 

 the water of this part of the North Atlantic, is affirmed by Admiral 

 Irminger as the result of the careful discussion he has made of the reckon- 

 ings kept by ships of the Danish Navy in their passages to and from 

 Iceland and Greenland ; the rate of that movement being estimated by him 

 at from 0'8 to 4*7 miles per day*. On the other hand, that beneath this 

 N.E. flow there is, in what I propose to call the "Lightning Channel," 

 between the Shetland and the Faroe Islands f, a S.W. flow of glacial 

 water which can scarcely have any other than a Polar source, appears to 

 me to be no less unmistakably proved by the observations recorded in my 

 Reports for 1868 and 1869. For if this glacial stream were not continually 

 being renewed from its Polar source, it could not retain its temperature of 

 from 32° to 29|° against the warmth imparted to it not merely by the 

 crust of the Earth beneath, but by the warm stream coming up against it. 

 And a further significant indication of its movement is afforded bv the 

 comparison of the two sets of Serial Soundings taken in the Cold Area 

 (Report for 1869, Proc. Roy. Soc. vol. xviii. p. 456); namely, No. 64 

 extending to a depth of 640 fathoms, and No. 52 at which the depth 

 was only 384. For although the latter Station was a degree to the 

 southward of the former, and its surface-temperature was 2°*4 higher, 

 the glacial stratum was sooner reached ; the stratum from 300 fathoms 

 to the bottom at 384 having a temperature between 30°'8 and 30°' 6, 

 which was only met with in No. 64 over its deeper bottom at a depth 

 of from 400 to 450 fathoms. This case, therefore, seems precisely 

 parallel to the creeping of Polar water up the sides and over the ridges 

 of submarine hills, of which the U.S. Coast Surveyors have obtained di- 

 stinct evidence in the Florida Channel (§§ 129-133) ; and it does not seem 

 explicable upon any other hypothesis, than that of a flow of the colder 

 stratum, which, if left at rest, would gravitate to the deeper part of the 

 channel. 



15. Proceeding still further North, we find this glacial stratum lying 

 nearer and nearer to the surface the nearer we approach the Polar ice- 

 barrier. This appears very clearly from the Temperature-soundings which 

 have been recently taken in the neighbourhood of Spitzbergen by M. Charles 

 Martins and by MM. Payer and Weyprecht ; these having effectually dis- 

 posed of the notion that the deeper water is warmer than the superficial, so 

 that the Thermometer rises as it descends. That such a rise not unfre- 

 quently presents itself to a limited extent is indubitable, the observations 



* Proceedings of the Royal Geographical Society, May 10, 18G9. 



t The discovery of the remarkable contrast between the bottom-temperatures met 

 with at like depths in adjacent areas of this Channel having been made by the Tempe- 

 rature-soundings taken in the 'Lightning' Expedition of 1868, it seems not inappro- 

 priate to give it the name of that Ship ; more especially as the ' Lightning ' has a further 

 historical interest, as one of the first two steam-vessels built in 1825 for the British Nav y 



