Storms, Lightning, and All the Other Fires that Ignite in the Air

Winds are created when the clouds dissolve into vapors.

The clouds can also sometimes descend so suddenly that they drive away violently all the air that is under them. This creatse a very strong but short-lived wind.

This is similar to a veil spread high in the air, then letting it descend flat towards the ground.

Heavy rains are almost always preceded by such a wind, which acts from top to bottom.

The wind’s coldness comes from those rain clouds, where the air is colder than that around us.

This wind causes swallows to fly very low, warning us of rain.

• It also brings down gnats which the swallows eat. Those gnats are used to fly in the high air when the weather is fine.

It is also he who sometimes, even when the cloud being very small, or descending only very little, is so weak that one hardly feels it in the open air, roaring down chimneys, makes the ashes and straws that are found in the corner of the fire dance, and excites there like little whirlwinds quite admirable for those who ignore the cause, and which are usually followed by some rain.

The descending cloud is very heavy and very extensive especially over large seas because the vapors are very evenly dispersed there.

This is why, as soon as the slightest cloud forms in some place, it immediately extends in all the other neighboring ones.

This infallibly causes a storm which is stronger, the larger and heavier the cloud is.

It lasts all the longer, the farther the cloud descends.

These squalls are made of those clouds which sailors fear so much in their great voyages, especially a little beyond the Cape of Good Hope.

There, the vapors that rise from the Ethiopian Sea, which is very wide and very heated by the sun.

They can easily cause a downwind stopping the natural course of the wind coming from the Indian Sea. It assembles them into a cloud.

The inequality between these two large seas and this land causes that cloud to become much larger than those which form in other regions where there are lesser inequalities between our plains, lakes, and mountains.

Almost no other clouds are ever seen in these places. As soon as the sailors there perceive some which begins to form, although it sometimes appears so small that the Flemings have compared it to an ox’s eye, from which they have given it the name, and that the rest of the air seems very calm and very serene, they hasten to lower their sails, and prepare to receive a storm, which always follows immediately.

And even I judge that it must be all the greater, the smaller this cloud has appeared at first. For not being able to become thick enough to obscure the air and be visible, without also becoming large enough, it can only appear so small because of its extreme distance; and you know that the higher a heavy body descends, the more impetuous is its fall.

Thus, this cloud being very high, and suddenly becoming very large and very heavy, descends entirely, driving away with great violence all the air that is under it, and causing by this means the wind of a storm.

The vapors, mixed among this air, are dilated by its agitation, and that there also come out for the time being several others from the sea, because of the agitation of its waves, which greatly increases the strength of the wind, and delaying the descent of the cloud, makes the storm last all the longer.

Then also that there are usually exhalations mixed among these vapors, which cannot be driven as far as them by the cloud, because their parts are less solid, and have more irregular figures, are separated from them by the agitation of the air, in the same way that, as it has been said above, by beating the cream, the butter is separated from the buttermilk.

In this way, they assemble here and there in various heaps, which floating always as high as possible against the cloud, finally come to be attached to the ropes and masts of the ships, when it finishes descending.

There being ignited by this violent agitation, they compose these fires named Saint Elmo’s, which console the sailors, and make them hope for good weather.

Often, these storms are in their greatest force towards the end, and that there may be several clouds one above the other, under each of which there are such fires; which may have been the reason why the ancients, seeing only one, which they called Helen’s star, esteemed it of bad omen, as if they had still then waited for the height of the storm.

Instead of which when they saw two, which they called Castor and Pollux, they took them for a good omen.

For it was ordinarily the most they saw, except perhaps when the storm was extraordinarily great they saw three, and esteemed them also on this account of bad omen.

However I have heard our sailors say that they sometimes see them to the number of four or five, perhaps because their ships are larger, and have more masts than those of the ancients, or that they travel in places where exhalations are more frequent.

For finally I can say nothing but by conjecture of what is done in the great seas that I have never seen, and of which I have only very imperfect relations.

There are storms that are accompanied by thunder, lightning, whirlwinds, and lightning.

These are caused by several clouds one being above the other. Sometimes, the highest descends very suddenly on the lowest.

As if the two clouds A and B being composed only of very rare and very extended snow, there is a hotter air around the upper A, than around the lower B.

The heat of this air can condense and weigh it down little by little. It can make the highest of its parts, beginning the first to descend, to beat down or drag with them a quantity of others, which will also fall all together with a great noise on the lower one.

In the same way that I remember having seen once before in the Alps, around the month of May, that

The snows when heated and weighed down by the sun, can create avalanches with the slightest movement of air.

They also produced the sound of thunder resounding in the valleys.

This is why it thunders more rarely in these regions in winter than in summer.

For so much heat does not easily reach the highest clouds then, to dissolve them.

And why, when during the great heats, after a North wind which lasts very little, one feels again a damp and stifling heat, it is a sign that it will soon follow thunder.

For this testifies that this north wind, having passed against the earth, has driven the heat towards the place of the air where the highest clouds form. Being then driven away, towards that where the lowest form, by the dilation of the lower air which the hot vapors it contains cause, not only the highest by condensing should descend, but also the lowest remaining very rare, and even being as if raised and repelled by this dilation of the lower air, should resist them in such a way that often they can prevent any part of it from falling to the ground.

The noise, which is made thus above us, is heard better because of the resonance of the air, and be greater by reason of the falling snow, than is that of avalanches.

Then note also that from this alone, that the parts of the upper clouds fall all together, or one after the other, or faster, or more slowly; and that the lower ones are more or less large, and thick, and resist more or less strongly, all the different sounds of thunder can easily be caused.

For the differences of lightning, whirlwinds, and lightning, they depend only on the nature of the exhalations that are found in the space that is between two clouds, and on the way that the upper falls on the other.

For if there have been great heats and droughts, so that this space contains a quantity of very subtle exhalations, and very disposed to ignite, the upper cloud cannot be almost so small, nor descend so slowly, that driving away the air which is between it and the lower, it does not make an éclair come out, that is to say, a light flame which dissipates itself at the same time. So that one can then see such lightning without hearing any noise of thunder; And even also sometimes without the clouds being thick enough to be visible.

As on the contrary if there are no exhalations in the air that are proper to ignite, one can hear the noise of thunder without any lightning appearing for that. And when the highest cloud falls only by pieces that follow each other, it causes only lightning and thunder; but when it falls whole and fast enough, it can cause whirlwinds and lightning with it.

Its extremities, such as C and D, must lower a little faster than the middle, since the air that is below, having less distance to travel to get out, yields to them more easily, and thus coming to touch the lower cloud, rather than the middle, it encloses a lot of air between them, as we see here towards E; then this air being pressed and driven with great force by this middle of the upper cloud which continues to descend, it must necessarily break the lower one to escape, as we see towards F; or open one of its extremities, as we see towards G.

When it has thus broken this cloud, it descends with great force towards the earth, then rises again in a whirlwind, because it finds resistance on all sides, which prevents it from continuing its movement in a straight line, as fast as its agitation requires.

Thus it composes a whirlwind; which may not be accompanied by lightning or lightning, if there are no exhalations in this air that are proper to ignite;

But when there are some, they all gather in a heap, and being driven very impetuously with this air towards the earth, they compose lightning. And this lightning can burn clothes and shave hair without harming the body, if these exhalations, which usually have the smell of sulfur, are only greasy and oily, so that they compose a light flame which only attaches to bodies that are easy to burn.

On the contrary, it can break bones without damaging the flesh, or melt the sword without spoiling the scabbard, if these exhalations being very subtle and penetrating, only participate in the nature of volatile salts or strong waters, by which means making no effort against bodies that yield to them, they break and dissolve all those which make them a lot of resistance. As we see strong water dissolve the hardest metals, and do not act against wax.