466 



Messrs. Carpenter, Jeffreys, and Thomson [Not. 18, 



37 (which was that of the 2435 fathoms' dredging), and to 6(r at Sta- 

 tion 34 : whilst it fell in the more Northerly Stations, which lay between 

 Lat. 53° 41' and 54" 53', to 54 3 8 at Station 19, to 53° 2 at Stations 17 

 and 18, though these were rather to the southward of the preceding, 

 and to 52 3, 2 at Station 12, which was yet farther south. A comparison 

 of the temperature of the Surface-water with that of the Air at each Station 

 indicates that a large part of the variation in the former is due, on the one 

 hand, to the heating effect of the solar rays, and on the other to the cool- 

 ing influence of winds. Thus at three Stations at which the Surface-tem- 

 peratures were 64" S, 65 5 6, and 66 c respectively, the thermometers in Air 

 showed 63 c- 5, 70", and 72 z ; whilst at four Stations at which the Surface- 

 temperatures ranged downwards from 54 C S to 52 : 2, the temperature of 

 the Air ranged from o5 z o to 53 = . In only one instance was the tempera- 

 ture of the Air decidedly lower than that of the Surface-water ; and this 

 was at Station 42, where, although the Surface-temperature was 62 = -6, the 

 temperature of the Air was only 59 z . But as this observation was made at 

 4 h 30" 1 on the morning of July 27, and as the wind was from the N.W., 

 the discrepancy may be regarded as accidental. 



10S. At thelast-meutioned Station, in Lat. 49 c 12'. about 250 miles to the 

 S.W.of Cork, a Series of Temperature-soundings was taken atevery lOfathoms 

 from the surface to 50 fathoms, with the view of determining the rate of ther- 

 mal decrease at successive depths in the superficial stratum. The total de- 

 crease in this descent amounted to 9 C, 4 ; the most rapid diminution being be- 

 tween 20 and 30 fathoms, within which vertical space the reduction amounted 

 toS 0 ^. In the next 1 0 fathoms it was only l c 6, and in the 1 0 following only 

 1°'2. Between 50 and 100 fathoms the total reduction was only 2°1 ; and 

 it may be fairly surmised that a large part of this occurred in the upper 

 20 fathoms ; for below 100 fathoms the rate of diminution becomes ex- 

 tremely slow, the total reduction between 100 and 500 fathoms being 

 only 3 C 7, or at an average of 0'9 per 100 fathoms. The rate of diminution 

 then again becomes more rapid, the total reduction between 500 and 800 

 fathoms being 5~4, or P S per 100 fathoms : and between 800 and 862 

 fathoms (bottom} there is a still more rapid diminution, a reduction of 

 2~'3 taking place in this comparatively small descent. 



109. On comparing with this the Series taken at every 100 fathoms at 

 Station 23, in Lat. 56" 13', we see a very close general accordance in the 

 rate of descent ; although the actual temperatures of the latter are from 2° 

 to 3" lower than those of the former at corresponding depths, as might be 

 expected from its higher Latitude. In the Surface-temperature, indeed, 

 the difference amounts to 5 C '3 ; but this becomes reduced to 2 C 6 at 100 

 fathoms, to Z°*5 at 200 fathoms, to 1°S at 300 fathoms, and to 1° 0 at 400 

 and 600 fathoms. The total reduction in the first 100 fathoms is here 

 8 0, 8, as against ll = 5 in the preceding case ; while the reduction between 

 100 and 500 is also rather less, being 2 Z 7. 



110. Extending the comparison to a Series taken still further northwards, 



