1872.] 



Currents in the Strait of Gibraltar. 



101 



drag, preventing it going to the N.W. as fast as it otherwise would. And 

 at one hour after low water the drag had drifted W. \ N. at a rate of 0*18 

 mile an hour, while the surface-current had stopped running, as shown hy 

 the buoys at anchor. 



Two hours after lowwater, the drag being placed at a depth of 1 08 fathoms, 

 10 fathoms above the bottom, immediately ran away with its buoy to the 

 westward, and drew it fast through the surface-water against a light west 

 wind, force 1 ; at the same time the anchored buoys showed a very slight 

 surface-current running to the S.W. Half an hour later the bottom 

 current-drag had drifted west 0*48 of a mile = 0*96 mile an hour, the cur- 

 rent itself at 1 *2 mile an hour. The surface-current was running to the west- 

 ward past the anchored buoys at an estimated speed of half a mile an hour. 



From this day's observations it appears that the bottom-water turned to 

 run to the westward a little before, and the surface-stratum at about an 

 hour after low water. 



On August 26, wind east, force 3, with a considerable swell from the 

 eastward, while making observations on the penetration of light at different 

 depths of water, some current-buoys were anchored in mid-channel 

 south of Europa Point, in 480 fathoms, to indicate the direction of the 

 surface- current. Half an hour before high water, when the current, if 

 affected by tide alone, should have been running to the westward, it was 

 found to be running towards the east at about half a mile an hour, indicated 

 by the lowest of three buoys floating 2 feet above water. During the next 

 2 hours, or until 1 j hour after high water, the lowest buoy was out of sight 

 and the second buoy had a slight strain on it, the tide estimated to be running 

 three quarters of a mile an hour. From 2| to 4 hours after high water 

 the second buoy swimming, with half its depth immersed, indicated a tide 

 of about 1 mile an hour. The pressure on the buoys now increased 

 sufficiently to sink two of them completely, and the strain proved to be 

 too much for the anchor, which was found to be shifting its position. 



At low water the current was running at its greatest speed, estimated to 

 be 3 miles an hour, with no appearance of changing. 



August 28. — Wind easterly, force 6, with a slight swell from the east- 

 ward. As the strongest current was expected to be found on the African 

 side of the Narrows, a position was taken up in the deep water from 2 to 3 

 miles north of Point Ceres. At 3| hours after low water, when the current 

 should have been running to the westward, a buoy anchored by a fine line 

 (to diminish the strain as much as possible) showed it to be running to the 

 eastward at an estimated speed of half a mile an hour, but from 1| hour 

 before high water to high water there was little or no movement of the 

 surface-water. 



At high water the surface-current again commenced running to the 

 eastward past the anchored buoys, and soon after the line was observed to 

 have been carried away. 



One hour and a half later the current-drag was lowered 225 fathoms, 



