POIETES, a Tyro in Fly-fishing.--PHYSICUS, an uninitiated
Angler, fond of inquiries in natural history, &c.--HALIEUS,
an accomplished fly-fisher.--ORNITHER, a sporting gentleman.

_Poietes_. I hope we shall have another good day to-morrow, for
the clouds are red in the west.

_Physicus_. I have no doubt of it, for the red has a tint of
purple.

_Halieus_. Do you know why this tint portends fine weather?

_Phys_. The air, when dry, I believe, refracts more red, or
heat-making rays; and as dry air is not perfectly transparent, they
are again reflected in the horizon. I have generally observed a
coppery or yellow sun-set to foretell 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.

_Hal_. I have often observed that the old proverb is correct--

A rainbow in the morning is the shepherd's warning:
A rainbow at night is the shepherd's delight.

Can you explain this omen?

_Phys_. A rainbow can only occur when the clouds containing or