of an aerial mountainous scene; hill capping hill, lighted up with an ever-varying light. When it is the harbinger of rain, its surface presents a fleecy appearance, and is formed in dense masses in lower strata of the atmosphere than usual. In fair weather, the cumulus has a well-defined rounded surface, and frequently increases or diminishes with the temperature, lasting in one form or the other throughout the whole day. Mr. Howard, speaking of this modification of clouds, says, "independently of the beauty and magnificence it adds to the face of nature, the cumulus serves to screen the earth from the direct rays of the sun; by its multiplied reflections, to diffuse, and, as it were, to economize the light; and also to convey the product of evaporation to a distance from the place of its origin. The connexion of the finer round forms, and more pleasing dispositions and colours of these aggregates, with warmth and calmness; and of every thing that is dark, and abrupt, and shaggy, and blotched, and horrid in them, with cold, and storm, and tempest, may be cited as no mean instance of the perfection of that wisdom and benevolence which formed and sustains them."

THE STRATUS.

The term stratus includes all those creeping mists which, during the night, and particularly in the summer, are seen to rise from low or damp situations. It is spoken of by writers as the lowest of all clouds: there are others, however, which, like itself, rest their lower surface upon the earth. The stratus generally rises after sunset, and vanishes soon after sunrise, being gradually separated from the earth, and ultimately evaporated. This modification has been long known as the harbinger of fair weather, and it is almost invariably followed by a serene and cheerful day.

THE CIRRO-CUMULUS.

The cirrus sometimes loses its fibrous character, and its streaks seem to contract and form themselves into globular or irregular masses, arranging themselves horizontally, and sinking in the atmosphere-this is the cirro-cumulus. It has been supposed by some, that this alteration of form results from the cessation, either from an alteration in its structure or in the condition of the air, of its office as the electrical conductor of the atmosphere. The cirro-cumulus is frequently

seen in dry summer weather, and, under certain circumstances, in the interval between showers. The nubecule of the cirro-cumulus sometimes almost cover the sky on a fine summer's evening, while at other times they are well defined, and far separated from each other. The varying forms of

this cloud are peculiarly beautiful; and there is no modification so likely to attract the attention of an observer of nature. But although it is usually the forerunner of fine weather, it is not always the indicator of peace; for when it makes its appearance with the cumulo-stratus, it is sure to be followed by a storm.

The cirro-stratus varies in form almost as much as the cirrus itself, from which it is frequently produced. It is, like the cirrus, a fibrous cloud, but the fibres are more dense, and generally more regular, than in that modification. Its appearance is commonly followed by rainy and windy weather. It is that modification in which the halo most frequently appears, and hence it is, in all probability, as Mr. Howard suggests, that this phenomenon has been considered a prognostic of foul weather. The cirro-stratus has, under certain circumstances, so much the appearance of shoals of fish, that it has

been called the mackerel-back sky. But at other times it presents a structure which warrants the designation, waved

cirro-stratus, and is then generally attended by high temperature and thunder-storms.

The cumulo-stratus is a compound modification, and being a common gradation between those clouds which indicate fair and those which bring rough and rainy weather, it is frequently seen in all those countries subject to sudden and repeated atmospheric changes. It consists of cirro-stratus blended with cumulus, and frequently appears as vast banks of cloud with overhanging masses. The ever-varying forms of this cloud are such as the painter durst not imitate, lest he should be charged with a mimicry of nature. We have often found amusement in the days of childhood, and in riper years, in tracing the outlines of well-known forms in burning embers, but these do not furnish half so prolific a field for the exercise of imagination as the cumulo-stratus. Here are pictured, in bold and determined outline, the ruined tower, with its heroes and demigods, the majestic mountain, giants, fairies, and scenes of by-gone days: but who can attempt its description?

that of a fungus with a thick stem. Its appearance may sometimes induce a casual observer to imagine the speedy fall of rain, but it is stated by Mr. Howard and others that rain never falls from the cumulo-stratus.

THE CUMULO-CIRRO-STRATUS, OR NIMBUS.

The nimbus has generally its origin in the cumulus. Vast masses of cumuli may, under favourable circumstances, M

be seen, in rough weather, previous to the fall of rain, to lift themselves into towering mountains of cloud, and by an insensible change to take the structure of the cumulo-stratus. After a short interval this modification becomes more dense, and increasing in irregularity and extent, forms itself into the nimbus or rain-cloud. It is worthy of remark, that when the cumulo-stratus is formed, lengthened masses of cirrostratus often cap it, and the quantity of rain seems to be in some degree proportional to the extent of the cirri.

There is no cloud that is so readily distinguished as the nimbus, and those who are least acquainted with the configuration and structure of clouds can generally detect it, although the cumulus and cumulo-stratus frequently assume a darker and more threatening aspect. Experience, however, guides us, and we frequently gain insensibly that knowledge which we cannot describe. We have often heard persons say that rain would fall from this, and not from that cloud, who yet have been unable to explain the reason of their opinions, always satisfying themselves with the assertion, I know it, I have seen it before."

Clouds are so often in an electrified condition, that Beccaria and others have thought that their formation is attribu