1868.] on Deep-sea Dr edgings. 171 



lead gave a minimum of 33° [0 o, 5 Cent.] and 34^-° [l°-4 Cent.] respectively, 

 the temperature of the surface-water being 52° [11°*1 Cent.]. 



10. This very remarkable indication was fully confirmed the next 

 morning, when we sounded again in lat. 60° 7' and long. 5° 21', and 

 found the depth to be 500 fathoms [914 metres], and the minimum 

 temperature, as given by the mean of three thermometers * (showing 

 3]i° [_0°-2 Cent.], 32° [0° Cent.], and 33° [0°*5 Cent.] respectively), to 

 be 32°*2 [0°'l Cent.], the temperature of the surface-water being 51° [10°'5 

 Cent.]. 



1 1 . We here for the first time had an opportunity of working our 

 Dredge at this great depth, and found no difficulty in doing so. The 

 bottom consisted of sand and stones ; and it is important to remark that 

 the same kind of bottom was met with in all our subsequent soundings 

 and dredgings in the "cold area" (§§ 12-14). — As might have been 

 anticipated from the extraordinary reduction of the Temperature, there 

 proved to be a comparative scantiness of Animal life ; and of the forms 

 which did present themselves, several belonged to the Boreal Fauna. 

 Still there were examples of several different groups ; and there was 

 not that predominance of low forms which some have supposed to cha- 

 racterize the Fauna of great depths. Indeed the Rhizopoda, of which 

 we afterwards encountered an extraordinary development at the like 

 depth, but in a much warmer temperature, were almost entirely absent. 

 It is worthy of note that a specimen of Astropecten of a bright red 

 colour came up adherent to the dredge-line at a distance of 250 fathoms 

 [457 metres] from the dredge, about 1200 fathoms [2195 metres) of line 

 being out. As this animal is entirely unprovided with swimming-organs, 

 and was found to be of such specific gravity as to sink immediately when 

 placed in a jar of sea-water, it can scarcely have been taken up anywhere 

 else than from the sea-bottom ; and if this be admitted, it is obvious that 

 at least 250 fathoms [457 metres] of the dredge-line must have been lying 

 on that bottom. Not only on many subsequent occasions did Ophiurida 

 come up on the like part of the dredge-line, but in our last dredging 

 (§ 19), from a depth of 650 fathoms [1189 metres], there came up at- 

 tached to it, at a distance of about 50 fathoms [92 metres] from the 

 dredge, two pieces of a Siliceous Sponge, which most assuredly could not 

 have been drawn from any other source than the sea-bottom f , and which 

 included many small living Ophiurida. 



* It had been our intention to make a careful comparison of each of these Thermometers 

 with an accurate standard on our return, and thus to have determined with greater pre- 

 cision the temperatures they respectively indicated ; but two of them were unfortunately 

 lost in a subsequent Sounding (§ 19). 



t From this it is obvious that the Dredge-rope, so far from buoying up the Dredge, 

 must effectually assist in sinking it, especially when the rope has been solidified by 

 previous repeated immersions at great depths. I find the specific gravity of a portion of 

 our dredge-rope, which has been thus subjected to a pressure of 118 atmospheres, to be 

 1347, that of Sea-water being about 1029. In our earlier dredgings, we attached one 

 or two couples of 12-lb. shot to the dredge-line at a short distance from the dredge, so as 

 VOL. XVII, O 



