§ 1. Between the flocks of small countless clouds which occupy the highest heavens, and the gray undivided film of the true rain-cloud, form the fixed masses or torn fleeces, sometimes collected and calm, sometimes fiercely drifting, which are, nevertheless, known under one general name of cumulus, or heaped cloud. The true cumulus, the most majestic of all clouds, and almost the only one which attracts the notice of ordinary observers, is for the most part windless; the movement of its masses being solemn, continuous, inexplicable, a steady advance or retiring, as if they were animated by an inner will, or compelled by an unseen power. They appear to be peculiarly connected with heat, forming perfectly only in the afternoon, and melting away in the evening. Their noblest conditions are strongly electric, and connect themselves with storm-cloud and true thunder-cloud. When there is thunder in the air, they will form in cold weather, or early in the day. § 2. I have never succeeded in drawing a cumulus. Its divisions of surface are grotesque and endless, as those of a mountain;--perfectly defined, brilliant beyond all power of color, and transitory as a dream. Even Turner never attempted to paint them, any more than he did the snows of the high Alps. Nor can I explain them any more than I can draw them. The ordinary account given of their structure is, I believe, that the moisture raised from the earth by the sun's heat becomes visible by condensation at a certain height in the colder air, that the level of the condensing point is that of the cloud's base, and that above it, the heaps are pushed up higher and higher as more vapor accumulates, till, towards evening, the supply beneath ceases; and at sunset, the fall of dew enables the surrounding atmosphere to absorb and melt them away. Very plausible. But it seems to me herein unexplained how the vapor is held together in those heaps. If the clear air about and above it has no aqueous vapor in it, or at least a much less quantity, why does not the clear air keep pulling the cloud to pieces, eating it away, as steam is consumed in open air? Or, if any cause prevents such rapid devouring of it, why does not the aqueous vapor diffuse itself softly in the air like smoke, so that one would not know where the cloud ended? What should make it bind itself in those solid mounds, and stay so:--positive, fantastic, defiant, determined?