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The cirri however frequently change to the cirrocumulus; and in the progrèss of the change the cirrous fibres seem to shoot out laterally into transverse and intersecting streaks, they first change to cirrocumulus at their points of intersection, which thicken, approach to the orbicular form, and seem like centres from which fibres eradiate; thus a sort of stelliform cirrocumulus is effected, which either goes on changing into a more perfect feature of that cloud, or changes again to cirrus or to cirrostratus, or evaporates. It often happens that, as the cloud is gently moving on, the spectator has not an opportunity of watching it throughout all its metamorphoses.

when he speaks of the "Lambeaux et fragments de nuages qui sont comme disseminés dans les differentes regions de l'air, les uns sont plus hauts (cirri, &c.) les autres plus bas (scud, &c.) et flottent au gre des vents de divers côtés." He speaks of them as vehicles of the electric fluid, and as useful in conveying away the matter of lightening, which would otherwise be oftener embodied in large clouds, and strike the earth with terrible violence. Thus he seems to have had some faint notion of an office performed by clouds, which more recent discoveries have ascribed to the cirrus. See Berthol.

De l'Elec. Met. t. II. p. 113.

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SECTION II.

Of the Varieties of the Sondercloud.

THE permanent features of any cloud should be distinguished from those which are only transitory, or which the cloud exhibits in the progress of its change from one modification to another. I have before noticed, that in the change from the cirrus to the cirrocumulus, a number of appearances present themselves, which cannot be referred to either. They generally, however, end in a determinable modification, which I call its permanent form; and in which it generally remains for some time, and then evaporates, or changes again. The permanent features of the cirrocumulus vary at different times, and the varieties are connected with particular states of the atmosphere. In fine warm weather in summer, particularly towards evening, the nubeculae which compose this cloud are often large, well defined, and separate from each other: the whole sky is sometimes replete with them. This feature is often the forerunner of fine and wholesome, after a long continuation of wet and variable,

weather it is strikingly contrasted to that variety of Sondercloud which is composed of very diminutive nubeculae; by which the sky seems sometimes peppered, if I may so express myself, with innumerable little round white specks, which are sometimes of so light a texture as to be almost transparent. There is a sort of cloud of this latter sort, which, though its nubeculae preserve something of the round shape of the cirrocumulus, has the light and flimsy appearance, and almost the transparency of cirrostratus of one kind, and it becomes very difficult to know what name to give it. Refer to the tenth section of this chapter.

In stormy weather, previous to thunder, a cirrocumulus often appears, whose component nubeculae are very dense and compact round bodies in very close arrangement. The prevalence of this feature, particularly when accompanied by cumulostratus, is a sure indication of an approaching storm.*

*If the cirrocumulus, as M. Howard supposes, be a cloud positively charged and very retentive of it, the intensity and decided character of this feature indicates the very high state of its charge; this notion agrees very well with the circumstance of its accompanying thunderstorms. Are not the densist Twainclouds formed from its conjunction with the cumulus ?

I have often had occasion to mention the cirrocumulus, as being very generally a foreboder of warmth. In Germany these clouds are called little sheep: and Professor Heyne has a note on them in his edition of Virgil.* And our poet Bloomfield has likewise compared them to a flock at rest, in a passage already cited. In certain weather cirrocumulus rapidly forms in different places in the sky, and soon subsides again, as mentioned in another place.

SECTION III.

Of the Varieties of the Wanecloud.

It would be impossible to convey to the reader a complete detail of all the varieties of any cloud; for, as in every other natural production, no two appear exactly similar in all particulars of shape, size, and situation. But as the clouds, countless and innumerable as their shapes and sizes are, have a tendency, under certain circumstances at present not precisely known, to break out into some of the seven

Heyne's Virgil, 4 vols. 8vo. Lips. 1803, and Georg. i. 97, p. 314 of vol. i.

distinct modifications; so each modification has certain particular varieties into which it forms itself on different occasions, and the meteorological speculator may be assisted, by having some of the principal of these pointed out to him.

The varieties of the cirrostratus are numerous; but throughout all of them this cloud preserves its distinguishing characteristics; namely, shallowness, and extent in proportion to the quantity of its substance; generally a horizontal position, and a tendency to alter its form and to subside. It is often lower down than a cirrus in the same sky, and a change from that cloud to cirrostratus is usually attended with a diminution of its altitude, a greater degree of density in its fibres, and in a more regularly horizontal position. The plane sheets of Wanecloud are the most simple of its forms; when these are not extensive, and are seen in the distance, they often look like a dense streak drawn along near to the horizon; but distinguishable from streaks of cirrus. There are some peculiar appearances of this kind, which, swelling somewhat in the middle, and seen below a more thin and extensive sheet of cloud, give the idea of the back of a great Dolphin rising out of the Ocean. It is in the thin and

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