distinctive of that season of the year. They are dry and parching,
every one being familiar with the unpleasant bodily sensations
attendant on this much-abused and yet most beneficent wind.
The _Etesian Winds_ are drawn from the north across the Mediterranean
by the great heat of the African desert. The _Mistral_ is a strong
north-west wind peculiar to the south-east of France. The _Pampero_ is
a north-west wind, blowing in summer from the Pampas of Buenos Ayres.
As long ago as the year 1600 Lord Bacon remarked that the
preponderating tendency of the wind was decidedly to veer _with_ the
sun’s motion, thus passing from N. through N.E., E., S.E., to south,
thence through S.W., W.N.W., to N.; also, that it often makes a
complete circuit in that direction, or more than one in succession
(occupying sometimes many days in so doing), but that it rarely backs,
and very rarely or never makes a complete circuit in the contrary
direction. The merit of having first demonstrated that this tendency is
a direct consequence of the earth’s rotation is due to Professor Dove,
of Berlin, who has also shown that the three systems of atmospheric
currents just treated of, viz., the constant, periodical, and variable
winds, are all amenable to the same influence.
As to the _mode_ of observing the wind, Admiral Fitzroy recommends that
a true east and west line should be marked _about the time of the
equinox_, and the north, south, and other points of the compass being
added, to take the bearings of the wind in relation to a dial so
prepared, the indications of the _lower_ stratum of clouds in
conjunction with vanes and smoke being preferred to any other.
The direction of the wind should always be given according to _true_,
and not to _compass bearings_. Two points to the westward nearly
represents the amount of “Variation of the Compass” for the British
Isles, which yields the following table for the conversion of
directions observed by the compass in Great Britain and Ireland to
approximate true bearings.
+---------------------+-----+-----+-----+-----+-----+-----+-----+
|Compass bearings. N | NNE | NE | ENE | E | ESE | SE | SSE |
|True bearings. NNW| N | NNE | NE | ENE | E | ESE | SE |
+---------------------+-----+-----+-----+-----+-----+-----+-----+
|Compass bearings. S | SSW | SW | WSW | W | WNW | NW | NNW |
|True bearings. SSE| S | SSW | SW | WSW | W | WNW | NW |
+---------------------+-----+-----+-----+-----+-----+-----+-----+
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