Page:The National geographic magazine, volume 1.djvu/196

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144
National Geographic Magazine.

ing about S. S. E. ½ E. for 7 hours and N. N. W. ½ W. for a little over 5 hours.

The first section investigated in 1888 was in the equatorial drift between Tobago and Barbados, where seven stations were occupied. The axis of the stream was found west of the middle, or nearer the South American shore, and the average direction was towards the north. At none of the stations did the current set in the direction of the wind, although the trades were blowing at all times with a force of from 2 to 7. The daily variation was also here very pronounced, the average time of maximum flow occurring about 5h 56m after the moon's transit. At 65 and 130 fathoms depth the current, at three of the stations occupied, was north-westerly; at one south-easterly. The velocity at 130 fathoms was greater than at 65 fathoms, and greater at the surface than at 15 and 30 fathoms.

At all of the three stations between Grenada and Trinidad tidal action was observed, with deflections due to local influences. The passage between Santa Lucia and St. Vincent appears to be in the line of the equatorial stream. At each of the five stations in this passage tidal action was pronounced, the currents setting in and out of the Caribbean Sea at some depth. The daily variation in this passage reaches a maximum at about 6h 3m after the moon's transit, and a minimum when the moon is on the meridian. The currents entering the Caribbean Sea through this passage are but 100 fathoms in depth, but there is probably an almost equal volume flowing out below that depth.

Between the Windward Islands the currents flow generally westward, but tidal action is everywhere apparent.

To the east of Desirade the currents at all observed depths have a northerly direction, fluctuating between about N. E. by E. to N. W. by N.

In the eastern part of the Anegada Passage the surface current flows into the Caribbean Sea in directions varying between S. S. W. and S. E., but the submarine current down to 130 fathoms flows in a direction lying between north and east.

In the more western part of the passage the currents are more complex, apparently on account of the greater variations in depth in the vicinity of the station occupied.

In the Mona Passage no regular currents were perceptible. Between Mona and Puerto Rico the currents observed set out of the Caribbean Sea, varying in direction from about W. by N.