[1] In South latitude the South wind corresponds to our North wind in
its nature and effects. The Easterly and Westerly winds retain their
respective peculiarities in both hemispheres.
[2] Exclusive of local land and sea breezes of hot climates.
[3] Glass, barometer, column, mercury, quicksilver, or hand.
[4] Or atmosphere, or the atmospheric fluid which we breathe.
[5] Or exhaustion.
[6] A vacuum.
[7] See pages 24 and 25.
[8] Thirty-two degrees is the point at which water begins to freeze, or
ice to thaw.
[9] Evaporation.
[10] The two thus combined making a hygrometer: for which some kinds of
hair, grass, or seaweed may be a make-shift.
[11] It stands lower, about a tenth of an inch for each hundred feet of
height directly upwards, or vertically, above the sea; where its average
height, in England, is 29·94 inches (at 32°).
[12] In an Aneroid, a metallic, or a wheel barometer, the hand's motion
should correspond to that of mercury in an independent instrument.
[13] Southerly in South latitude.
[14] In the best columns, those of standards for example, no concavity
is seen, at any time: but it is otherwise with many barometers, which do
show a concavity.
[15] In these cases there is usually a combination or a contest of
currents in the atmosphere, horizontally, _or_ one _above_ the other, or
diagonally.
[16] Thunder clouds sometimes rise and spread against the wind
(lower-current). It is probable that there is a meeting, if not a
contest of air currents, electrically different, whenever lightning is
seen. Their concurrence, when the new one advances from _polar_ regions,
does not depress the barometer, except in oscillations of the mercury,
which are very remarkable at some such times.
[17] Aneroids, metallic barometers, and oil sympiesometers, seem to be
much more affected than mercurial barometers by electrical changes.
[18] Southerly, in North latitude; the reverse in the Southern
hemisphere.
[19] A "high dawn" is when the first indications of daylight are seen
above a bank of clouds. A "low dawn" is when the day breaks on or near
the horizon. The first streaks of light being very low.
[20] Indications of weather, afforded by colours, seem to deserve more
critical study than has been often given to the subject. Why a rosy hue
at sunset, or a grey neutral tint at that time, should presage the
reverse or their indications at sunrise;--why bright yellow should
foretell wind at either time, and pale yellow, wet;--why clouds seem
soft, like water colour; or hard edged, like oil paint, or Indian ink on
an oily plate;--and why such appearances are infallible signs--are yet
to be shown satisfactorily to practical men.
[21] In the trade winds of the tropics there is usually a counter
current of air, with light clouds,--which does not indicate any
approaching change. In middle latitudes such upper currents are not so
evident, except before a change of weather.
[22] _Much_ refraction is a sign of Easterly wind. _Remarkable_
clearness is a bad sign.
[23] The "young moon with the old moon in her arms" (Burns, Herschel,
and others) is a sign of bad weather in the temperate zones or middle
latitudes, because (probably) the air is then exceedingly clear and
transparent.
[24] Even in ordinary changes of weather it is interesting, as well as
useful, to mark the formation or disappearance of clouds, caused by
colder and warmer currents of air mixing: or intermingling.
[25] Depending on pressure and temperature.
[26] Sir James Ross--M. Daussy.
[27] Williwaw (Whirl-awa?) of the old sealers and whalers.
[28] Seamen call the light sails, used only in very fine weather,
"flying kites."
[29] Herschel.
[30] Dové.
[31] For a barometer of this kind, Admiral Milne has invented
self-registering mechanism, that answers well.
[32] A small turnscrew being applied gently to the screw head at the
back. This is often necessary, on receiving or first using an aneroid
that has long been lying by, or that has been shaken by travelling.
[33] It is a good weather glass--to be suspended on or near the upper
deck, for easy reference;--and is unlikely to be injured by mere
concussion of air, or vibration of wood, when guns are fired.
[34] Allowing 0,0011 of an inch for each foot.
[35] The manufacture of these useful auxiliary instruments (all French
originally) has increased much latterly: and now the patent has expired.
They might be so improved so to be worth more than double their present
value.
[36] Like the sun's edge or limb, touching the sea horizon, as seen
inverted when using a sextant.