182 



Messrs. Carpenter and Jeffreys on 



[Dec. 8, 



to resume our experiments the next morning in the shallowest part of the 

 Strait. 



65. The average Surface-temperature of the Mid-stream during our 

 outward passage through the Strait proved to be 66°, thus corresponding 

 exactly with what we had found it to be on our inward passage seven 

 weeks previously (§ 30). This depression, as compared with the surface- 

 temperature of the Strait itself nearer the shore, both north and south, 

 and with the temperature of the Mediterranean to the eastward and that 

 of the Atlantic to the westward, is extremely remarkable. "We shall here- 

 after inquire how it is to be explained (§ 74). 



66. The breadth of the Channel between Capes Spartel and Trafalgar 

 (Chart II.) is about 23 nautical or 26 J statute miles. Its northern half 

 is much shallower than the southern, as is shown in Section b b ; the 

 100-fathom line off the Spanish coast running at about twelve miles' 

 distance from Cape Trafalgar, whilst along the African coast it keeps much 

 nearer the shore, being at only two miles' distance from Cape Spartel. 

 Between these two lines, the greatest depth marked in the Chart is 194 

 fathoms ; and this occurs off Cape Spartel, at less than a mile from the 

 100-fathom line. Between this and the opposite border of the deeper 

 channel, the depths vary from 130 to 180 fathoms ; the abruptness of the 

 differences at neighbouring points indicating a rocky bottom, of which we 

 soon had unpleasant experience. 



Stations 65, 66. 







No. 2, -- 





West - - '■ . 



' u — 



• -JZOfalh. 



- - - . East 







Wol 







' — 'Surface. 









'~~-—<jV!>.3 









lOOfctth. 



' - 1 







^- Wind . 









\Nd. J 









\- ■-: - \Force3 





1 



South' 







Rate (per hour) and Direction of Movement of Surface-float and of Current-drag at 

 different Depths ; with Force and Direction of Wind in No. 3. (No Wind in 

 Nos. 1, 2.) 



67. We commenced our observations on the morning of Oct. 1st at the 

 point of greatest depth (Station 65). The temperature of the surface at 

 6 a.m. was only 63°, which was at least eight degrees lower than the 

 average temperature at that hour within the Mediterranean. The bottom- 

 temperature at 198 fathoms was 54°*5, and the Specific Gravity of the 

 bottom-water was 1 028"2. The coincidence both in temperature and Sp. Gr. 

 with the bottom-water at Station 64 was thus very close. The place of 



