102 



Capt. G. S. Nares on the 



[Jan. 18, 



when its attached buoy immediately started off, moving towards the east 

 much faster than the surface-current. Angles taken to positions on shore 

 showed that the drag was moving to the eastward 2*1 miles an hour. 



Subsequent observations, made on the south side of the ridge of shallow 

 water between Capes Spartel and Trafalgar, and in the Narrows south of 

 Tarifa, confirmed the foregoing results, and showed that while the surface- 

 current was running east 1 and 2 miles an hour, the bottom-current was moving 

 in the same direction from 2* 4 to 2* 6 miles. Somewhat later, the under-current 

 at 50 fathoms and the surface-current were found to have the same rate of 

 speed, namely 3*8 miles an hour. Differences of rate then took place, but 

 the current maintained its direction and tidal character ; and as the rate of 

 the under-current gradually decreased, there is no reason to suppose that it 

 did not turn to run to the westward at low water. The quicker movement 

 of the under-current at the early part of the tide may have been due to 

 retardation of the surface-current by a strong breeze from the east. For 

 all practical purposes the bottom-current below 100 fathoms may be re- 

 garded as uniform. The current was found to turn with the tide, and to 

 vary its rate in accordance with the progress of the ebb or the flow. 



In concluding his report, Captain Nares remarks that on the 28th a much 

 stronger east-running bottom current was experienced, which he attributes 

 to the observations on that day being made in the position where the 

 easterly in-set runs strongest ; but it may have been occasioned by a reflux 

 of water into the Mediterranean stronger than usual to replace that blown 

 to the westward during the previous east winds, which the swell denoted 

 had been blowing strongly a day or two before. For the first two hours of 

 the ebb-tide the bottom-current ran to the eastward faster than the surface- 

 current, the same as observed on the 28th. 



The strong west-running under-current of 1*8 mile an hour thus shown 

 to exist in the Narrows where the inflow of the Atlantic stream retards the 

 surface-current most, agrees fairly with the slower movement of 1*2 mile 

 an hour in the broader and shallower part to the westward, where the 

 surface-water is less affected. 



In the Narrows the last of the ebb and first of the flood sets across from 

 Tarifa towards Point Ceres, joining the inshore current running to the 

 westward along that shore. 



These observations show that the under-current in the narrowest part of 

 the Strait is affected by tidal influence, the same as the water on the shallow 

 ridge to the westward. But the eddies, which would naturally be expected 

 at this part, in consequence of the funnel-shaped mouth of the Strait, 

 complicate the movements and prevent such exact demonstrations as those 

 found further to the westward, where the current stream runs more steadily. 



The Report will shortly be published in full by the Admiralty. 



