1872.] 



On the Cmrents in the Strait of Gibraltar. 



97 



January 18, 1872. 

 GEORGE BIDDELL AIRY, C.B., President, in the Chair. 



Pursuant to notice given at the last Meeting, Mr. Spottiswoode proposed 

 and Admiral Richards seconded the Right Hon. George Joachim Goschen, 

 First Lord of the iidmiralty, for election and immediate ballot. 



The ballot having been taken, Mr. Goschen was declared duly elected. 



The following communication was read : — ■ 



' Investigations of the Currents in the Strait of Gibraltar, made 

 in August 1871, by Captain G. S. Nares, R.N., of PI. M.S. 

 ' Shearwater/ under Instructions from Admiral Richards, 

 P.R.S., Hydrographer of the Admiralty." Communicated 

 by Admiral Richards. Received December 28, 1871. 



In fulfilment of instructions to afford to Dr. Carpenter, F.R.S., who was 

 rittached to the ' Shearwater,' every opportunity to investigate the Gibraltar 

 current, and to " use every effort to set the question at rest," Captain 

 Nares spent six days, from August 22nd to the 30th, in examining the 

 currents and taking soundings and observations of temperature in the Strait 

 of Gibraltar. The details and results, embodied in a report, were delivered 

 to the Admiralty, and, by favour of Admiral Richards, have furnished ma- 

 terial for the following summary. 



"While the observations were being made, east winds, force to 6*, were 

 experienced : they were reported as having also prevailed during the pre- 

 vious fortnight. 



The movement of water in the Strait was found to be tidal, affected by 

 a surface-current running into the Mediterranean from the Atlantic. The 

 ebb-tide, which is a combination of the two streams running in the same 

 direction, sets to the eastward, and at a rate considerably faster than the 

 flood-tide, which is caused by the two streams meeting, and which runs to 

 the westward. 



In the Narrows, in the middle of the Strait, the surface-water is affected 

 by tidal influence, but not to so great an extent as the water inshore ; for 

 the east-running current from the Atlantic being here collected into an ex- 

 tremely narrow and strong-running stream, it is only during easterly winds 

 and calms that a decided set to the westward is enabled to manifest itself; 

 during westerly winds the tidal set to the westward is doubtless frequently 

 overpowered by the extra strength of the in-running Atlantic current, and 

 no set to the westward can be expected ; at the same time there must be a 

 considerable diminution of the east-running current during the flood-tide. 

 In the Narrows the actual distance run by the surface-water towards the 



