The Botanic Garden, a Poem in Two Parts. Part 1: the Economy of VegetationDarwin, Erasmus
History
The Botanic Garden, a Poem in Two Parts. Part 1: the Economy of Vegetation
Darwin, Erasmus
Natural history; Plants -- Poetry; Portland Vase
1. This great quantity of air can not be supplied by superior currents
passing in a contrary direction from south to north, because such
currents must as they arise into the atmosphere a mile or two high
become exposed to so great cold as to occasion them to deposit their
moisture, which would fall through the inferior current upon the earth
in some part of their passage.
2. The whole atmosphere must have increased in quantity, because it
appears by the barometer that there exists one-fifteenth part more air
over us for many weeks together, which could not be thus accumulated by
difference of temperature in respect to heat, or by any aerostatic laws
at present known, or by any lunar influence.
From whence it would appear that immense masses of air were set at
liberty from their combinations with solid bodies, along with a
sufficient quantity of combined heat, within the polar circle, or in
some region to the north of us; and that they thus perpetually increase
the quantity of the atmosphere; and that this is again at certain times
re-absorbed, or enters into new combinations at the line or tropical
regions. By which wonderful contrivance the atmosphere is perpetually
renewed and rendered fit for the support of animal and vegetable life.
SOUTH-EAST WINDS.
The south-east winds of this country consist of air from the north which
had passed by us, or over us, and before it had obtained the velocity of
the earth's surface in this climate had been driven back, owing to a
deficiency of air now commencing at the polar regions. Hence these are
generally dry or freezing winds, and if they succeed north-east winds
should prognosticate a change of wind from north-east to south-west; the
barometer is generally about 30. They are sometimes attended with cloudy
weather, or rain, owing to their having acquired an increased degree of
warmth and moisture before they became retrograde; or to their being
mixed with air from the south.
2. Sometimes these south-east winds consist of a vertical eddy of north-
east air, without any mixture of south-west air; in that case the
barometer continues above 30, and the weather is dry or frosty for four
or five days together.
It should here be observed, that air being an elastic fluid must be more
liable to eddies than water, and that these eddies must extend into
cylinders or vortexes of greater diameter, and that if a vertical eddy
of north-east air be of small diameter or has passed but a little way to
the south of us before its return, it will not have gained the velocity
of the earth's surface to the south of us, and will in consequence
become a south-east wind.--But if the vertical eddy be of large
diameter, or has passed much to the south of us, it will have acquired
velocity from its friction with the earth's surface to the south of us,
and will in consequence on its return become a south-west wind,
producing great cold.
NORTH-WEST WINDS.
Public-domain text, read in full here on John Shaqi.
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