FullReads

When I was a boy I used to wonder if the clouds were hollow and carried their water as in a cask, because had we not often heard of clouds bursting and producing havoc and ruin beneath them? The hoops gave way, perhaps, or the head was pressed out. Goethe says that when the barometer rises, the clouds are spun off from the top downward like a distaff of flax; but this is more truly the process when it rains. When fair weather is in the ascendant, the clouds are simply reabsorbed by the air; but when it rains, they are spun off into something more compact: ’tis like the threads that issue from the mass of flax or roll of wool, only here there are innumerable threads, and the fingers that hold them never tire. The great spinning-wheel, too, what a humming it makes at times, and how the footsteps of the invisible spinner resound through the cloud-pillared chambers!

The clouds are thus literally spun up into water; and were they not constantly recruited from the atmosphere as the storm-centre travels along,–was new wool not forthcoming from the white sheep and the black sheep that the winds herd at every point,–all rains would be brief and local; the storm would quickly exhaust itself, as we sometimes see a thunder-cloud do in summer. A storm will originate in the far West or Southwest–those hatching-places of all our storms–and travel across the continent, and across the Atlantic to Europe, pouring down incalculable quantities of rain as it progresses and recruiting as it wastes. It is a moving vortex, into which the outlying moisture of the atmosphere is being constantly drawn and precipitated. It is not properly the storm that travels, but the low pressure, the storm impulse, the meteorological magnet that makes the storm wherever its presence may be. The clouds are not watering-carts, that are driven all the way from Arizona or Colorado to Europe, but growths, developments that spring up as the Storm-deity moves his wand across the land. In advance of the storm, you may often see the clouds grow; the condensation of the moisture into vapor is a visible process; slender, spiculae-like clouds expand, deepen, and lengthen; in the rear of the low pressure, the reverse process, or the wasting of the clouds, may be witnessed. In summer, the recruiting of a thunder-storm is often very marked. I have seen the clouds file as straight across the sky toward a growing storm or thunder-head in the horizon as soldiers hastening to the point of attack or defense. They would grow more and more black and threatening as they advanced, and actually seemed to be driven by more urgent winds than certain other clouds. They were, no doubt, more in the line of the storm influence. All our general storms are cyclonic in their character, that is, rotary and progressive. Their type may be seen in every little whirlpool that goes down the swollen current of the river; and in our hemisphere they revolve in the same direction, namely, from right to left, or in opposition to the hands of a watch. When the water finds an outlet through the bottom of a dam, a suction or whirling vortex is developed that generally goes round in the same direction. A morning-glory or a hop-vine or a pole-bean winds around its support in the same course, and cannot be made to wind in any other. I am aware there are some perverse climbers among the plants that persist in going around the pole in the other direction. In the southern hemisphere the cyclone revolves in the other direction, or from left to right. How do they revolve at the equator, then? They do not revolve at all. This is the point of zero, and cyclones are never formed nearer than the third parallel of latitude. Whether hop-vines also refuse to wind about the pole there I am unable to say.