In his shepherd’s calling he was prompt, And watchful more than ordinary men. Hence had he learned the meaning of all winds, Of blasts of every tone; and oftentimes, When others heeded not, he heard the South Make subterraneous music, like the noise Of bagpipes upon distant Highland hills. The late Sir Humphry Davy, one of the most successful modern explorers of the secrets of nature, was not above attending to, and explaining, the “weather-omens” which are derived from popular observation. In his _Salmonia_ he has the following dialogue between Haliens, (a fly-fisher,) Poietes, (a poet,) Physicus, (a man of science,) and Ornither, (a sportsman):— _Poiet._—I hope we shall have another good day to-morrow, for the clouds are red in the west. _Phys._—I have no doubt of it, for the red has a tint of purple. _Hal._—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 refracted in the horizon. I have generally observed a coppery or yellow sunset 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 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 depositing the rain are opposite 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 those clouds is passing from us. _Poiet._—I have often observed that when the swallows fly high, fine weather is to be expected or continued; but when they fly low, and close to the ground, rain is almost surely approaching. Can you account for this? _Hal._—Swallows follow the flies and gnats, and flies and gnats usually delight in warm strata of air; and as warm air is lighter, and usually moister, than cold air, when the warm strata of air are high, there is less chance of moisture being thrown down from them by the mixture with cold air; but when the warm and moist air is close to the surface, it is almost certain that, as the cold air flows down into it, a deposition of water will take place.