The National Geographic Magazine, Vol. I., No. 2, April, 1889 — John Shaqi
The National Geographic Magazine, Vol. I., No. 2, April, 1889Various
History
The National Geographic Magazine, Vol. I., No. 2, April, 1889
Various
Geography -- Periodicals
Off Cape Hatteras the Blake accomplished the remarkable feat of
remaining at anchor in 1,852 fathoms, and this with a surface current
of over 4 knots. Two stations were occupied, and similar variations in
velocity were observed as at the other stations. The notable feature at
this station was the discovery of tidal action beneath the Gulf Stream,
the currents at 200 fathoms depth changing their direction very
regularly, the average current flowing 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 5^h 56^m 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 6^h 3^m 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.
Public-domain text, read in full here on John Shaqi.
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