1 869.] 



on the Scientific Exploration of the Deep Sea. 



431 



54. The general result of this series of Soundings is of the highest inte- 

 rest ; and although it may be premature to attempt an explanation of the 

 details of the phenomena until all the temperature- observations which have 

 been made in the North Atlantic have been reduced to the Miller-Casella 

 standard and carefully correlated, still certain general conclusions seem 

 self-evident. — The high surface-temperature, reduced by 13 J degrees at 

 250 fathoms, is undoubtedly due to superheating by the direct heat of the 

 sun. This is shown more clearly by the Table (§ 58), where nearly 7° 

 are seen to be lost between the surface and 30 fathoms, and 4° more 

 between 30 fathoms and 100 fathoms. — From 100 to 500 fathoms the 

 temperature is still high and tolerably uniform, and it falls rapidly between 

 500 and 1000 fathoms; a reference to the second Table shows that the 

 rapid fall is between 650 and 850 fathoms, during which interval there 

 is a loss of nearly 6°. The second stage of elevated temperature, from 

 250 to 650 fathoms, seems to be caused by the north-easterly reflux of 

 the great equatorial current. From 1000 fathoms the loss of heat goes on 

 uniformly at the rate of 0 o, 5 for every 250 fathoms. The most singular 

 feature in this decrease of temperature for the last mile and three quarters 

 is its absolute uniformity, which appears to be inconsistent with the idea 

 of a current, unless it were one of excessive slowness. It appears that the 

 presence of this vast underlying body of comparatively cold water can 

 only be accounted for on the supposition of a general interchange of warm 

 and cold water, according to the doctrine laid down by Dr. Carpenter in 

 the c Lightning ' Report, which will be more fully expounded hereafter 

 (§ H5). 



55. We were now steaming slowly back towards the coast of Ireland ; and 

 on Monday, July 26, we dredged in depths varying from 557 to 584 fathoms 

 (Stations 39-41) in ooze, with a mixture of sand and dead shells. In these 

 dredgings we got one or two very interesting Alcyonarian zoophytes, and 

 several Ophiuridans, including Ophiothrix fragilis, Amphiura Ballii, and 

 Ophiacantha spinulosa. Many of the animals were most brilliantly phospho- 

 rescent ; and we were afterwards even more struck by this phenomenon in 

 our Northern Cruise. In some places nearly everything brought up seemed 

 to emit light, and the mud itself was perfectly full of luminous specks. The 

 Alcyonarians, the Brittle-stars, and some Annelids were the most brilliant. 

 The Pennatulte, the Virgularia, and the Gorgonice shone with a lambent 

 white light, so bright that it showed quite distinctly the hour on a watch. 

 The light from Pavonaria quadrangularis was pale lilac, like the flame of 

 cyanogen ; while that from Ophiacantha sjrinulosa was of a brilliant green, 

 confiscating from the centre of the disk, now along one arm, now along 

 another, and sometimes vividly illuminating the whole outline of the star- 

 fish. 



56. The question of the amount and the kind of Light in these abysses 

 was constantly before us. That there is light, there can be no doubt. The 

 eves in many species of all classes were well developed ; in some, very 



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