180 



Messrs. Carpenter and Jeffreys on 



[Dec. 8, 



being 460 fathoms instead of 517 ; but the bottom-temperature was a little 

 lower, being 54°* 7 instead of 55°-5. The respective Specific Gravities of 

 the Surface- and Bottom-waters, and of that of the Intermediate stratum of 

 250 fathoms, were found to coincide almost exactly with those previously 

 determined, as the following comparative statement shows : — 



Now the density of the bottom-water here corresponds so exactly with 

 that which prevails over the deeper bottom of the Western basin of the 

 Mediterranean, whilst it so considerably exceeds that of the bottom- as well 

 as of the .swr/ace-water of the Atlantic, that we cannot fail to recognize it 

 as belonging to the Mediterranean basin ; so that, if it has any motion at 

 all, we should expect that motion to be from east to west. Still more cer- 

 tainly may this be affirmed of the intermediate stratum, the density of 

 which corresponds with that of the bottom-water of the shallower part of 

 the Mediterranean basin ; the greatest depth (586 fathoms) at which such 

 water was obtained being at Station 40, the nearest point to the Strait from 

 which a specimen of bottom-water was obtained (§ 43). And it may be 

 further predicated that a stratum of water of a density of 1029*3 could not 

 overlie water of the density of 1028*1, unless it moved over the stratum 

 below,— that is, unless (1 ) the two strata were moving in opposite directions, 

 or (2) were moving at different rates in the same direction, or (3) the upper 

 stratum were in motion in either direction, and the lower stratum were 

 stationary. It will presently appear that the second of these conditions is 

 the one which obtains in the present case. 



62. We now proceeded to repeat our experiments with the "current- 

 drag," with the view of obtaining, if possible, unequivocal evidence of the 

 existence of that Westerly undercurrent which so many considerations 

 combined to render probable. — The direction of the Wind during this set 

 of experiments was from the East, or opposite to that of the surface-current ; 

 and its force (3 to 4) was sufficient, by its meeting the current, to produce 

 a considerable swell, which necessitated the employment of a larger boat, 

 and rendered it unsafe to allow her to drift without men. The sectional 

 area of the boat was therefore greater than on the former occasion, giving 

 the in-current a stronger hold upon her; but, on the other hand, the 

 surface she presented to the wind was also greater; and as this acted* in 

 the opposite direction, the latter increase might be considered to neutralize 

 the former, or even rather to exceed it, so as to render the boat more 

 capable of being carried westwards by the "current-drag," if this should be 

 acted on by an outward undercurrent. The rate of surface-movement was 

 tested as before (§ 36), and proved to be 1-823 mile per hour, its direction 



Specific Gravity, 



Specific Gravity. 



Surface . . . 

 250 fathoms 

 Bottom . . . 



Station 39. 

 1027*1 

 1029-3 

 1028-1 



Station 64. 



1027- 1 

 1029-2 



1028- 3 



