"But it is not the outline only which is thus systematically false. The drawing of the solid form is worse still; for it is to be remembered that, although clouds of course arrange themselves more or less into broad masses, with a light side and a dark side, both their light and shade are invariably composed of a series of divided masses, each of which has in its outline as much variety and character as the great outline of the cloud; presenting, therefore, a thousand times repeated, all that I have described as the general form. Nor are these multitudinous divisions a truth of slight importance in the character of sky, for they are dependent on, and illustrative of, a quality which is usually in a great degree overlooked--the enormous retiring spaces of solid clouds. Between the illumined edge of a heaped cloud and that part of its body which turns into shadow, there will generally be a clear distance of several miles--more or less, of course, according to the general size of the cloud; but in such large masses as Poussin and others of the old masters, which occupy the fourth or fifth of the visible sky, the clear illumined breadth of vapour, from the edge to the shadow, involves at least a distance of five or six miles. We are little apt, in watching the changes of a mountainous range of cloud, to reflect that the masses of vapour which compose it are linger and higher than any mountain-range of the earth; and the distances between mass and mass are not yards of air, traversed in an instant by the flying form, but valleys of changing atmosphere leagues over; that the slow motion of ascending curves, which we can scarcely trace, is a boiling energy of exulting vapour rushing into the heaven a thousand feet in a minute; and that the topling angle, whose sharp edge almost escapes notice in the multitudinous forms around it, is a nodding precipice of storms, three thousand feet from base to summit. It is not until we have actually compared the forms of the sky with the hill-ranges of the earth, and seen the soaring alp overtopped and buried in one surge of the sky, that we begin to conceive or appreciate the colossal scale of the phenomena of the latter. But of this there can be no doubt in the mind of any one accustomed to trace the forms of cloud among hill-ranges--as it is there a demonstrable and evident fact--that the space of vapour visibly extended over an ordinarily clouded sky is not less, from the point nearest to the observer to the horizon, than twenty leagues; that the size of every mass of separate form, if it be at all largely divided, is to be expressed in terms of _miles_; and that every boiling heap of illuminated mist in the nearer sky is an enormous mountain, fifteen or