When travelling across the prairies, we may, at times, when gazing upwards at the sky, see what appears to be a vast cloud approaching from the horizon. It is produced by infinite swarms of locusts, or grasshoppers, as they are called in North America. [From Professor Hind's "Red River Exploring Expedition."] About noon they appear to lessen perceptibly the rays of the sun. The whole horizon wears an unearthly ashy hue, from the light reflected by their transparent wings. The air is filled as with flakes of snow. The clouds of insects, forming a dense body, cast a glimmering, silvery light from altitudes varying from 500 to 1000 feet. The sky, as near the sun as its light will allow us to gaze, appears continually changing colour, from blue to silvery white, ashy grey, and lead colour, according to the numbers in the passing clouds of insects. Opposite to the sun, the prevailing hue is a silvery white, perceptibly flashing. Now, towards the south, east, and west, it appears to radiate a soft, grey-tinted light, with a quivering motion. Should the day be calm, the hum produced by the vibration of so many millions of wings is quite indescribable, and more resembles the noise popularly termed "a ringing in one's ears," than any other sound. The aspect of the heavens during the period that the greatest flight is passing by is singularly striking. It produces a feeling of uneasiness, amazement, and awe, as if some terrible unforeseen calamity were about to happen. When the grasshoppers are resting from their long journeys, or in the morning when feeding on the grass and leaves, they rise in clouds as we march through the prairie; and when the wind blows, they become very troublesome, flying with force against our faces, and into the nostrils and eyes of the horses, filling every crevice in the carts. Fortunately, comparatively few take flight on a windy day, otherwise it would be impossible to make headway against such an infinite host in rapid motion before the wind, although composed individually of such insignificant members. The portions of the prairie visited by the grasshoppers wear a curious appearance. The grass may be seen cut uniformly to one inch from the ground. The whole surface is covered with the small, round, green exuviae of these destructive invaders. They frequently fly at an enormous height above the earth. An engineer engaged in the Nebraska survey, mentions that, when standing on the summit of a peak of the Rocky Mountains, 8500 feet above the level of the plains in Nebraska--being 14,500 feet above that of the sea--he saw them above his head as far as their size rendered them visible.