How Clouds Form

Clouds can form at various distances from the ground, depending on how high the vapors rise before they condense enough to form clouds.

This is why we often see several layers of clouds, sometimes even moving with different winds. This phenomenon is more common in mountainous regions because the heat that raises the vapors acts more unevenly there than elsewhere.

Moreover, the highest clouds are almost never composed of water droplets but only ice particles because the air at those altitudes is colder, or at least as cold as that at the summits of high mountains, which is cold enough to prevent snow from melting even in the height of summer.

The higher the vapors rise, the colder it gets, which freezes them, and the less they are pressed by winds. Hence, the uppermost parts of clouds usually consist of very fine ice filaments dispersed far apart in the air.

Below this, small ice knots or clusters form, covered in tiny hairs, and progressively, slightly larger ones form below them. Finally, at the lowest levels, water droplets sometimes form.

When the air containing these particles is completely calm or uniformly carried by a wind, both the droplets and ice particles can remain dispersed and unordered, making the shape of the clouds indistinguishable from fog.

However, when winds that do not evenly occupy the surrounding air push these clouds, they cannot move uniformly, causing the clouds to be pressed and forced into the shape that least obstructs their movement.

This makes the cloud surfaces flat and smooth. A particular point of interest is that all the small snow knots or clusters on these surfaces arrange themselves so that each has six others around it, touching or at least equally distant from it.

For example, suppose a wind comes from the western part D over the land AB, opposing the usual air course, or if you prefer, another wind comes from the eastern part C.

These 2 winds stopped at the beginning, one the other, in about the space FGP, where they condensed some vapors, of which they made a confused mass, while their forces balancing and finding themselves equal in this place, they left the air calm and tranquil.

Two winds are often opposed in this way. This is because:

• there are always several different clouds around the earth at the same time
• each cloud usually extends its course, without turning aside, until it meets a contrary cloud that resists it.

Their forces cannot remain balanced there for a long time. Their matter flowing there more and more if they do not both cease together, which is rare.

The strongest finally takes its course by:

• the bottom, or
• the top
• the middle
• all around the cloud.

This depends on what it is more disposed to.

If the stronger cloud does not completely quench the weaker cloud, it at least constrains it to turn aside.

Suppose that the western wind blows between G and P, has forced the Eastern one to pass underneath towards F, where it has caused the fog that was there to fall into dew, then has retained above itself the cloud G, which, finding itself pressed between these two winds, has become very flat and extended

The small ice pellets that were on its surface, both above and below, as well as on the underside of the cloud P, must have arranged themselves in such a way that each one has six others surrounding it.

For one cannot imagine any reason that would have prevented them from doing so, and naturally all round and equal bodies that are moved in the same plane, by a force that is sufficiently similar, arrange themselves in this way, as you can see by experience, by throwing a row or two of round, unstrung pearls confusedly onto a plate, and shaking them, or only blowing a little against them so that they approach each other.

I am only talking here about the surfaces of the bottom or top, and not about the sides, because the unequal amount of matter that the winds can push against or remove from each side at any given moment makes the shape of their circuit ordinarily very irregular and unequal.

I also do not add that the small ice knots that compose the inside of the cloud G should be arranged in the same way as those of the surfaces, because this is not at all so obvious.

But I want you to consider again those that can go and stop under it, after it is fully formed.

For if, while it remains suspended in space G, some vapors come out of the places on the earth that are towards A, which cool in the air little by little and are converted into small ice knots, which the wind drives towards L, there is no doubt that these knots must arrange themselves in such a way that each of them is surrounded by six others, which press it equally, and are in the same plane; and thus compose first of all like a sheet that extends under the surface of this cloud, then another sheet that extends under this one, and so on of others, as much as there will be matter.

The wind, which passes between the earth and this cloud, acting with more force against the lowest of these sheets than against the one immediately above, and with more force against this one than against the one still above, and so on, can drag them along, and make them move separately from each other, and thus polish their surfaces by knocking down on both sides the small hairs that are around the pellets of which they are composed.

Even it can make a part of these sheets slip out from under this cloud G, and transport them beyond, as towards N, where they compose a new one.

Although I have only spoken here of the ice particles that are piled up in the form of small knots or pellets, the same can also be easily understood of the water droplets, provided that the wind is not strong enough to make them push each other, or that there are some exhalations around them, or, as often happens, some vapors not yet disposed to take the form of water, which separate them.

For otherwise, as soon as they touch each other, several of them come together in one and thus become so large and so heavy that they are forced to fall as rain.

The shape of each cloud’s perimeter is usually very irregular and uneven—should only be understood for those clouds that occupy less space in height and width than the surrounding winds.

For sometimes, there is such an abundance of vapors at the point where two or more winds meet that they force these winds to swirl around them instead of passing above or below. This creates an extraordinarily large cloud, which, being equally pressed on all sides by these winds, becomes completely round and very smooth in its circumference.

Additionally, when these winds are somewhat warm, or when the cloud is exposed to the heat of the sun, it can develop a kind of crust or shell of many ice particles joined together. This crust can become quite thick and heavy without causing the cloud to fall, because the entire rest of the cloud supports it.