figure, increases irregularly upward, grows more dense, and overhangs its base in uneven or rugged folds a pre-existing cirrus, cirrocumulus, or cirrostratus, or one perhaps immediately formed for the occasion, alights on its summit, and inosculates. The cumulostratus varies in appearance: sometimes it overhangs a perpendicular stem, and looks like a great mushroom; frequently a long range of cumulostrati appear together, which have the appearance of a chain of mountains with silvery tops. Before thunder-storms it seems frequently reddish, which some have imagined to arise from its being highly charged with the electric fluid. 7. Nimbus.-Clouds of any one of the abovementioned modifications, at the same degree of elevation, may increase so much as completely to obscure the sky two or more different modifications may also do the same thing in different elevations, and the effect of this obscuration may be such as would induce an inattentive observer to expect the speedy fall of rain. It appears, however, from attentive observation, that no cloud effuses rain until it has previously undergone a change sufficiently remarkable to constitute it a distinct modification, to which the term nimbus has not inaptly been applied. The best time for viewing the progress of nimbification is by stormy weather; cumuli may then be seen rising into mountains and becoming cumulostrati, while long strata of cirrostratus permeate their summits; and the whole phenomenon has the appearance of a range of mountains, transfixed by the mighty shafts of giants. After having existed some while in this form, they become large and irregular, and they get darker by intensity, till all seem concentrated in a dense black mass, with a cirrose crown extending from the top, and ragged cumuli entering from below, and eventually the whole resolves itself into rain. According to Mr. Howard's theory, the origin of clouds is from the surface of the earth and waters. That the vapour upraised by the accession of the diurnal temperature, in the manner described, is condensed into a visible cloud, either by cold, or by the air, from other causes; losing its power of holding so much water in solution as before; or by the joint influence of these causes. That cumuli are the immediate result of this process; and that in the evening, when the heat is diminished, the air deposits its vapour again in the form of dew, which gravitates to the ground, becoming more dense as it approaches the earth, because the lower atmosphere is now the coolest; and finally lodges on the surface of the herbage, or of the ground, where it awaits the reascending sun to be again evaporated. Cumuli also are represented to be dispersed, and their constituent particles to come to the ground in the same manner. According to the same theory, it appears that the other modifications are also the consequence of vapour carried up into the atmosphere, while their peculiarities are more immediately effected by the agency of the electric fluid. We shall conclude with a brief review of the modifications ascending from the Stratus, formed by the condensation of vapour on its escape from the surface to the Cumulus, collecting its water in the se cond stage of its ascent, both probably existing by virtue of a positive eletricity. From these proceeding through the partially conducting Cumulostratus to the Cirrostratus and Cirrocumulus; the latter positively charged, and considerably retentive of its charge; the former less perfectly insulated, and, perhaps, conducting horizontally; we arrive thus at the region where the Cirrus, light and elevated, obeys every impulse or invitation of that fluid, which, while it finds a conductor, ever operates in silence; but which, embodied and insulated in a denser collection of watery atoms, sooner or later bursts its barrier, leaps down in lightning, and glides through the Nimbus from its elevated station to the earth. For further information on this interesting subject, we refer the inquisitive student to The Philosophical Magazine, vol. xvi; Ree's Cyclopedia, art. CLOUD; and particularly to Mr. Forster's very ingenious Researches about Atmospheric Phenomena, just published; to which last work we are indebted for some of our preceding observations. II. RULES FOR PREDICTING CHANGES IN THE WEATHER. § i. Prognostics from the Atmosphere, Winds, &c. 1. A south wind or great heat in summer portends a whirlwind, Job xxxvii, 9. 2. Cold or fair weather is indicated by the north wind, which drives away rain, Job xxxvii, 9, 22. 3. A red sky in the evening foretels fair weather; in the morning, foul, Matthew xvi, 2. The evening red and morning grey, Is a sign of a fair day. A red evening and a grey morning sets the pilgrim a walking. 4. A cloud rising out of the west indicates rain, Luke xii, 54. 5. A south wind is a sign of heat, Luke xii, 54. 6. If clouds appear white, and drive to the northwest, it is a sign of several days' fair weather; and thus Pliny, If the rising sun be encompassed with an iris, or circle of white clouds, and they disperse equally, this is a sign of fair weather. If woolly fleeces spread the heavenly way, Be sure no rain disturbs the summer day. 7. If in the evening a white mist be spread over a meadow contiguous to a river, it will be evaporated by the Sun's rays on the following morning, and is an indication of fine weather throughout the day; so in the morning, if a mist, which is impending over low lands, draw off towards those which are more elevated, it announces a fine day. 8. 9. In the decay of the moon, A cloudy morning bodes a fair afternoon. 10. The gradual diminution of clouds till they can be no longer seen in the air, is a sign of fine weather; so likewise is the continuance of abundant dew upon the grass after a serene day. 11. The approach of bad weather may be known by the clouds gathering and lowering; and by the sky, after serene weather, becoming undulated, as it were, with small clouds. 12. If red the sun begins his race, Or, as the same effect is more elegantly described by Virgil: Above the rest the sun, who never lies, Foretels the change of weather in the skies, 13. During winter, if the clouds appear not unlike fleeces, i. e. thick and close in the middle, and very white at the edges, the surrounding sky being remarkably blue, they indicate hail or snow, or cold, chilling showers of rain. 14. Where the clouds appear moving in two opposite currents, and the lower current is wafted rapidly before the wind, it is a certain sign of rain; and, if they occur during summer, or generally in hot weather, they announce thunder storms. 15. Thunder is mostly preceded by hot, and followed by cold and drizzling or showery weather. 16. The west wind is usually damp, on account of the vast quantity of vapours it collects in its progress over the Atlantic Ocean : the south wind, which blows from the torrid zone, is the warmest of the four, as the north wind is the coldest, while the east wind is the most dry; but if rain fall during the prevalence of an easterly wind, it may be expected to continue, with little intermission, for four and twenty hours. We shall conclude this section with some illustrations from the prince of Roman poets. Observe the daily circle of the sun, And the short year of each revolving moon: If Aurora, with half opened eyes, And a pale sickly cheek, salutes the skies; But more than all, the setting sun survey, But if with purple rays he brings the light, |