1869.] 



on the Scientific Exploration of the Deep Sea. 



455 



200, 300, 400, 500, 600, and 767 fathoms (bottom) respectively, with the ' 

 result of showing a reduction of only 1 1°"2 at the last-mentioned depth ; 

 in the second, which was near the S.E. border of the Faroe Bank, the 

 temperature was taken at every 50 fathoms down to 300, and then at 384 

 fathoms (bottom), showing a reduction of 2 1°'5 ; while in the third, which was 

 nearly midway between the Faroe and the Shetland Islands, the temperature 

 was taken at every 50 fathoms down to 600, and then at 640 fathoms 

 (bottom), showing a reduction of 20 0, 1 . Of these Serial Soundings there 

 were in all 26, making, with the 36 Bottom-soundings, a total of 62. 



95. With these results, obtained with Thermometers upon which complete 

 reliance can be placed, those obtained last year with the best ordinary 

 Thermometers are found to be in close accordance, when the proper cor- 

 rection for pressure is applied to them. Thus No. 47 Sounding of the 

 'Porcupine' having been taken in almost exactly the same spot of the 

 Warm area as No. xn. of the ' Lightning,' — namely, on what we now 

 call the " Holtenia-gtoxmO." (§ 61), — the former gave 43°*8 as the mini- 

 mum temperature at 542 fathoms, while the latter gave 4/°*3 as the mini- 

 mum at 530 fathoms : and the difference of 3°'5 exceeds by scarcely more 

 than a degree — which may be a mere seasonal variation — the error 

 (about 2°*1) which the pressure of water at that depth would produce 

 in the unprotected thermometers. On the other hand, No. 55 Sound- 

 ing of the ' Porcupine ' having been taken in the same part of the 

 Cold area as No. viii. of the 'Lightning,' — the distance between the 

 two being only about 8 miles, — the former gave 29°*8 as the minimum 

 at 605 fathoms, while the latter gave 32° as the minimum at 550 

 fathoms ; and the difference of 2°*2 is exactly equivalent to the correc- 

 tion for pressure at that depth in the unprotected thermometers. Thus 

 the difference between the two 'Lightning' Soundings in the Warm 

 and Cold areas respectively having been 15 0, 3, the difference between 

 the two corresponding 'Porcupine' Soundings was 14°. This very near 

 accordance gave us, of course, a feeling of great satisfaction in our last 

 year's work ; and it fully justified our conclusion that whatever might be 

 the pressure-correction required by the instruments then employed, it 

 would not affect the differences obtained at nearly approximating depths. 

 It further justifies us in assuming the correctness (when thus rectified) of 

 the minimum temperatures taken last year at stations considerably west- 

 ward of the ground over which we worked in the ' Porcupine.' 



96. The data thus obtained respecting the Temperatures at different 

 Depths in the Warm and Cold areas respectively, are correlated in Table I., 

 which includes, with the three sets of Serial Soundings, all the Bottom- 

 sounding that accord with them. The localities of the several Soundings 

 are indicated by their Numbers in Diagram III. 



