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
The antiquity of the appearance of northern lights has been doubted; as
none were recorded in our annals since the remarkable one on Nov. 14,
1574, till another remarkable one on March 6, 1716, and the three
following nights, which were seen at the same time in Ireland, Russia,
and Poland, extending near 30 degrees of longitude and from about the
50th degree of latitude over almost all the north of Europe. There is
however reason to believe them of remote antiquity though inaccurately
described; thus the following curious passage from the Book of
Maccabees, (B. II. c. v.) is such a description of them, as might
probably be given by an ignorant and alarmed people. "Through all the
city, for the space of almost forty days, there were seen horsemen
running in the air, in cloth of gold, and armed with lances, like a band
of soldiers; and troops of horsemen in array encountering and running
one against another, with shaking of shields and multitude of pikes, and
drawing of swords, and casting of darts, and glittering of golden
ornaments and harness."
NOTE II.--PRIMARY COLOURS.
_Cling round the aerial bow with prisms bright,
And pleased untwist the sevenfold threads of light._
CANTO I. l. 117.
The manner in which the rainbow is produced was in some measure
understood before Sir Isaac Newton had discovered his theory of colours.
The first person who expressly shewed the rainbow to be formed by the
reflection of the sunbeams from drops of falling rain was Antonio de
Dominis. This was afterwards more fully and distinctly explained by Des
Cartes. But what caused the diversity of its colours was not then
understood; it was reserved for the immortal Newton to discover that the
rays of light consisted of seven combined colours of different
refrangibility, which could be seperated at pleasure by a wedge of
glass. Pemberton's View of Newton.
Sir Isaac Newton discovered that the prismatic spectrum was composed of
seven colours in the following proportions, violet 80, indigo 40, blue
60, green 60, yellow 48, orange 27, red 45. If all these colours be
painted on a circular card in the proportions above mentioned, and the
card be rapidly whirled on its center, they produce in the eye the
sensation of white. And any one of these colours may be imitated by
painting a card with the two colours which are contiguous to it, in the
same proportions as in the spectrum, and whirling them in the same
manner. My ingenious friend, Mr. Galton of Birmingham, ascertained in
this manner by a set of experiments the following propositions; the
truth of which he had preconceived from the above data.
1. Any colour in the prismatic spectrum may be imitated by a mixture of
the two colours contiguous to it.
2. If any three successive colours in the prismatic spectrum are mixed,
they compose only the second or middlemost colour.
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