DOI Page / Citation link:
https://doi.org/10.11588/diglit.2086#0165
PICTORIAL PHENOMENA OF NATURE. 143
plete semicircle, if the rain cloud is sufficiently extensiTe to display it. Its extent
diminishes as the solar altitude increases, because the coloured arch is a portion of
a circle whose centre is a point in the sky directly opposite to the sun. Above the
height of forty-five degrees the primary bow is invisible; and hence, in our climate,
the rainbow is not seen in summer about the middle of the day. In peculiar
positions a complete circle may be beheld, as when the shower is on a mountain,
and the spectator in a valley; or when viewed from the top of a lofty pinnacle,
nearly the whole circumference may sometimes be embraced. When rain is abun-
dant, there is a secondary bow distinctly seen, produced by a double reflection.
This is exterior to the primary one, and the intervening space has been observed to
be occupied by an arch of coloured light. The secondary bow differs from the
other, in exhibiting the same series of colours in an inverted order. Thus the red
is the uppermost colour in the interior bow, and the violet in the exterior. The
same lovely spectacle may be seen when the solar splendour falls upon the spray of
the cataract and the waves, the shower of an artificial fountain, and the dew upon
the grass."
When rain has ceased, and sunshine succeeded, the effect produced by the
passing shower may be shown by the freshness and glistering of the green leaves,
the unusual reflection on the road, steam rising from rocks or places bare of verdure
when the hot sun has burst forth, and, in addition, the more easily noticed incidents
occasioned by rain, as the posture and grouping of cattle or figures that may have
sought shelter from the sudden shower. Sir Humphrey Davy's " Salmonia" contains
also some remarks on the rainbow and the colour of clouds. He considers that
when clouds are red with a tint of purple in the west at sunset, the next day will
be fine, because the air, when dry, refracts more red, or heat-making rays; and as
dry air is not perfectly transparent, they are again reflected in the horizon. A
coppery or yellow sunset foretells rain; but as an indication of wet weather
approaching, nothing is more certain than a halo round the moon, which is produced
by the precipitated water; and the larger the circle the nearer the clouds, and,
consequently, the more ready to fall. In explanation also of the old proverb,
" A rainbow in the morning is the shepherd's warning;
A rainbow at night is the shepherd's delight,"
he informs us, " that a rainbow can only pccur when the clouds containing or
depositing the rain are opposite to the sun, and in the evening the rainbow is in
the east, and in the morning in the west; and as our heavy rains in this climate are
usually brought by the westerly wind, a rainbow in the west indicates that the bad
weather is on the road, by the wind, to us; whereas the rainbow in the east proves
that the rain in these clouds is passing from us."
plete semicircle, if the rain cloud is sufficiently extensiTe to display it. Its extent
diminishes as the solar altitude increases, because the coloured arch is a portion of
a circle whose centre is a point in the sky directly opposite to the sun. Above the
height of forty-five degrees the primary bow is invisible; and hence, in our climate,
the rainbow is not seen in summer about the middle of the day. In peculiar
positions a complete circle may be beheld, as when the shower is on a mountain,
and the spectator in a valley; or when viewed from the top of a lofty pinnacle,
nearly the whole circumference may sometimes be embraced. When rain is abun-
dant, there is a secondary bow distinctly seen, produced by a double reflection.
This is exterior to the primary one, and the intervening space has been observed to
be occupied by an arch of coloured light. The secondary bow differs from the
other, in exhibiting the same series of colours in an inverted order. Thus the red
is the uppermost colour in the interior bow, and the violet in the exterior. The
same lovely spectacle may be seen when the solar splendour falls upon the spray of
the cataract and the waves, the shower of an artificial fountain, and the dew upon
the grass."
When rain has ceased, and sunshine succeeded, the effect produced by the
passing shower may be shown by the freshness and glistering of the green leaves,
the unusual reflection on the road, steam rising from rocks or places bare of verdure
when the hot sun has burst forth, and, in addition, the more easily noticed incidents
occasioned by rain, as the posture and grouping of cattle or figures that may have
sought shelter from the sudden shower. Sir Humphrey Davy's " Salmonia" contains
also some remarks on the rainbow and the colour of clouds. He considers that
when clouds are red with a tint of purple in the west at sunset, the next day will
be fine, because the air, when dry, refracts more red, or heat-making rays; and as
dry air is not perfectly transparent, they are again reflected in the horizon. A
coppery or yellow sunset foretells rain; but as an indication of wet weather
approaching, nothing is more certain than a halo round the moon, which is produced
by the precipitated water; and the larger the circle the nearer the clouds, and,
consequently, the more ready to fall. In explanation also of the old proverb,
" A rainbow in the morning is the shepherd's warning;
A rainbow at night is the shepherd's delight,"
he informs us, " that a rainbow can only pccur when the clouds containing or
depositing the rain are opposite to the sun, and in the evening the rainbow is in
the east, and in the morning in the west; and as our heavy rains in this climate are
usually brought by the westerly wind, a rainbow in the west indicates that the bad
weather is on the road, by the wind, to us; whereas the rainbow in the east proves
that the rain in these clouds is passing from us."