204 



Messrs. Carpenter and Jeffreys on 



[Dec. 8, 



valence of particular winds. "We have been informed by Admiral Oramaney 

 that, according to his own experience, the inset is most considerable towards 

 the African coast, while the outset occasionally observed (§ 106) is most 

 decided on the Northern coast ; and this statement derives very remarkable 

 confirmation from the Thermometric observations already detailed. For 

 these show that the lower temperature of the m-current is specially notice- 

 able near Cape Spartel (§ 73) ; whilst the higher temperature, which is 

 traceable westwards along the Spanish and Portuguese coasts as far as Cape 

 St. Vincent, and there suddenly falls to the ordinary standard of the Atlantic, 

 seems to be derived from an efflux of the Mediterranean water (§ 75). 



105. The length of the narrower portion of the Strait (see Chart II.), 

 sometimes distinguished as the Gut, is about 35 miles. Its width, which 

 is about 22 miles between Capes Trafalgar and Spartel, gradually diminishes 

 to somewhat more than 9 miles between Tarifa and Alcazar point ; and 

 then increases until it reaches 1 2 miles between Gibraltar and Ceuta, east- 

 ward of which the Strait terminates abruptly in the wide basin of the Medi- 

 terranean. The deepest portion of the Strait is at its eastern extremity ; 

 its depth between Gibraltar and Ceuta reaching 517 fathoms, and averaging 

 about 300 (Section c d.). From this the bottom gradually but irregularly 

 slopes upwards (Section a b) as far as the western extremity of the Gut, 

 where the shallowest water is to be found. The northern half of the 

 channel across the section between Capes Spartel and Trafalgar (Section e f) 

 scarcely anywhere exceeds 50 fathoms ; whilst its southern half does not 

 seem anywhere to reach 200, and may be considered to average 150 fathoms. 

 On the Atlantic side of this ridge the bottom gradually slopes downwards, 

 until it reaches, at 40 miles westward, a depth about equal to that which 

 it has between Gibraltar and Ceuta. This ridge, therefore, constitutes a 

 kind of marine " watershed," separating the Inland basin of the Medi- 

 terranean from the great Oceanic basin of the Atlantic. 



106. Through the central part of this Strait a current almost invariably 

 sets eastward, or from the Atlantic into the Mediterranean. This current 

 is most rapid in the narrower part of the Gut, where the mflow usually 

 has a rate of from two to three miles an hour ; this rate sometimes rising 

 to four miles, or even occasionally (as stated by Gibraltar pilots to Admiral 

 Smyth) to five; whilst the current is sometimes so reduced in speed as to 

 be scarcely perceptible, even giving place (though very rarely) to a con- 

 trary movement or onflow from the Mediterranean towards the Atlantic. 

 These variations are partly due to Tidal influence, which is here very de- 

 cided, and which may either concur with or oppose the general current. 

 When the tide is flowing, its motion is westwards, or in opposition to the 

 current; and at spring- tide this motion maybe sufficiently powerful to 

 check the current, or even to reverse its direction for a short time. When 

 the tide is ebbing, on the other hand, its motion is eastwards, or in the 

 direction of the current ; and it is to the ebb of spring-tides that the occa- 

 sional augmentation in the rate of the current to 5 miles an hour is probably 



