When Mr. Loudon was at Schwetzingen, Rhenish Bavaria, in 1829, he witnessed in the post-house there for the first time what he afterwards frequently saw--an amusing application of zoological knowledge for the purpose of prognosticating the weather. Two tree-frogs were kept in a crystal jar about eighteen inches high and six inches in diameter, with a depth of three or four inches of water at the bottom, and a small ladder reaching to the top of the jar. On the approach of dry weather the frogs mounted the ladder, but when moisture was expected they descended into the water. These animals are of a bright green, and in their wild state climb the trees in search of insects, and make a peculiar singing noise before rain. In the jar they got no other food than now and then a fly; one of which, Mr. Loudon was assured, would serve a frog for a week, though it would eat from six to twelve flies in a day if it could get them. In catching the flies put alive into the jar the frogs displayed great adroitness. Snails are extraordinary indicators of changes in the weather. Several years ago, Mr. Thomas, of Cincinnati, known as an accredited observer of natural phenomena, published some interesting accounts of Weather-wise Snails. They do not drink (he observes), but imbibe moisture in their bodies during rain, and exude it at regular periods afterwards. Then a certain snail first exudes the pure liquid; when this is exhausted, a light red succeeds, then a deep red, next yellow, and lastly a dark brown. The snail is very careful not to exude more of its moisture than is necessary. It is never seen abroad _except before rain_, when we find it ascending the bark of trees and getting on the leaves. The tree-snail is also seen ascending the stems of plants _two days before rain_: if it be a long and hard rain they get on the sheltered side of the leaf, but if a short rain the outside of the leaf. Another snail has the same habits, but differs only in colour: before rain it is yellow, and after it blue. Others show signs of rain, not only by means of exuding fluids, but by means of pores and protuberances; and the bodies of some snails have large tubercles rising from them _before rain_. These tubercles commence showing themselves ten days previous to the fall of rain they indicate; at the end of each of these tubercles is a pore; and at the time of the fall of rain these tubercles, with their pores opened, are stretched to their utmost to receive the water. In another kind of snail, a few days before rain appears a large and deep indentation, beginning at the head between the horns, and ending with the jointure at the shells. Other snails, a few days before the rain, crawl to the most exposed hill-side, where, if they arrive before the rain descends, they seek some crevice in the rocks, and then close the aperture of the shell with glutinous substance; this, when the rain approaches, they dissolve, and are then seen crawling about.