The Grains of Hail

I do not determine how many such grains each one can be divided into.

But it seems that for the ordinary, it must be at least 8. They can also perhaps be divided into 12, 20, 24, 32, or even a much larger number, according to their size, and of a more subtle snow, and that the cold, which converts them into hail, is harsher and comes more suddenly.

And I have observed more than once such hail, the grains of which had roughly the shape of the segments of a ball divided into 8 equal parts by three intersecting sections at right angles at the center.

Then I also observed others, which being longer and smaller, seemed to be about a quarter of those there, although their corners, having become blunt and rounded by tightening, they almost had the shape of a sugar loaf.

I also observed that before or after, or even among these hailstones, there commonly fell some others that were round.

For even though I took special care to do so, I could never find two that held together.

But I soon satisfied myself on this matter, by considering how the wind always agitates, and successively bends all the parts of the surface of the water, by flowing over it, without making it rough or uneven for that.

For I knew from this that it infallibly bends and ripples the surfaces of clouds in the same way, and that by continually moving each ice particle a little differently from its neighbors, it does not allow them to stick together completely, even though it does not dislodge them for that, and yet does not fail to flatten and polish their small surfaces: in the same way that we sometimes see it polish the waves, which it does in the dust of a campaign.

After this cloud came another, which produced only small roses or wheels, with 6 teeth rounded in semicircles, such as are seen towards Q, and which were all transparent, and all flat, about the same thickness as the blades that had preceded them, and the best cut and compassed, that it is possible to imagine.

Even I perceived in the middle of some of them a very small white point, which one could have said was the mark of the foot of the compass which had been used to round them.

But it was easy for me to judge that they had been formed in the same way as these blades, except that the wind having pressed them much less, and the heat having perhaps also been a little less, their points had not melted completely, but only a little shortened, and rounded at the end in the shape of teeth.

And for the white point that appeared in the middle of some of them, I did not doubt that it came from the fact that the heat, which had made them transparent from white, had been so moderate that it had not penetrated at all to their center.

There followed many other such wheels, joined two by two by an axle, or rather, because at first these axles were very thick, one could have said that they were as many small crystal columns, each end of which was adorned with a six-petaled rose a little wider than their base.

But there fell afterwards more delicate ones, and often the roses or stars that were at their extremities were unequal. Then there fell also shorter ones, and still shorter ones by degrees, until finally these stars joined together completely, and there fell doubles with 12 points or rays long enough and perfectly well compassed, some equal, and others alternately unequal, as seen towards F and towards E.

And all this gave me occasion to consider that the ice particles, which are of two different planes or sheets laid one on top of the other in the clouds, can be attached together more easily than those of the same sheet.

For although the wind, acting usually more strongly against the lowest of these sheets than against the highest, makes them move a little faster, as has just been noted: nevertheless it can also sometimes act against them with equal force, and make them ripple in the same way: especially when there are only two or three of them one on top of the other, and then sifting through the surroundings of the pellets that compose them, it makes those of these pellets, which correspond in different sheets, always remain as if immobile opposite each other, notwithstanding the agitation and rippling of these sheets, because by this means the passage is easier for it.

Yet the heat, being no less prevented by the proximity of the pellets of two different sheets, from melting those of their hairs which look at each other, than by the proximity of those of the same, only melts the other surrounding hairs, which immediately mix among those which remain, and freeze again, compose the axles or columns which join these small pellets, at the same time that they change into roses or stars.**

Winter in 1635

On February 4, 1635, after an extremely cold spell, it rained a bit in the evening in Amsterdam, where I was.

The rain turned into a thin layer of ice upon hitting the ground, followed by very fine hail.

I judged that the grains were about the size represented near H. They were drops of the same rain that had frozen high in the air.

However, instead of being perfectly round as raindrops, they were noticeably flatter on one side, resembling the shape of the crystalline humor of our eye.

This made me realize that the wind, which was very strong and very cold at the time, had the power to alter the shape of the drops as they froze.

What surprised me the most was that among the last grains that fell, I noticed some with 6 small teeth around them, similar to the cogs of clock wheels, as you can see near I.

These teeth were very white, like sugar, whereas the grains, being transparent ice, appeared almost black.

These teeth were made of very fine snow that had adhered around them since they had formed, much like hoarfrost clings to plants.

I understood this clearly because I found one or two grains surrounded by numerous tiny hairs composed of paler and finer snow than the small teeth around the others. It could be compared to the ash that covers embers as they burn compared to the compacted ash in a hearth.

I struggled to imagine how these 6 teeth could have been so precisely arranged around each grain in the middle of free air during the agitation of a strong wind. I realized that this wind could have easily carried some of these grains below or beyond a cloud and held them there, as they were small enough.

There, they must have arranged themselves in such a way that each one was surrounded by 6 others situated on the same plane, following nature’s usual order.

Moreover, the heat in the upper atmosphere which caused the rain also moved some vapors that the same wind drove against these grains shortly before, where they froze into very fine hairs, possibly even helping to support them.

Thus, they could easily remain suspended there until some warmth returned.

This warmth melted all the hairs around each grain except those directly opposite the center of one of the six surrounding grains, as their coldness prevented the heat’s action.

The melted hairs then mixed among the 6 remaining clusters, reinforcing them and making them less penetrable to heat, causing the melted material to freeze among them and form these 6 teeth.

In contrast, the numerous hairs I saw around some of the last fallen grains were not affected by this heat at all.

The next morning at 8am, I observed yet another type of hail or rather snow that I had never heard of before.

These were small, flat, highly polished, very transparent ice plates, about the thickness of a sheet of thick paper and the size shown near K.

But they were so perfectly cut into hexagons with six straight sides and six equal angles that it is impossible for humans to make anything so exact.

I quickly realized that these plates must have first been small ice clusters arranged as I mentioned earlier. They were pressed by a very strong wind accompanied by enough heat to melt all their hairs and fill all their pores with the moisture from the melted hairs.

This turned them from white to transparent.

At the same time, the wind pressed them so tightly together that no space remained between them. This smoothed their surfaces by passing over and under them, thus precisely shaping them into these plates.

The only small difficulty was that these ice clusters were partially melted and pressed together. They did not stick to each other, but remained separate.

I was not surprised at the size, which I had noticed at the beginning in these columns. Although I knew well that the matter of the small hairs, which had been around 2 pellets, could not have been enough to compose them.

For I thought that there had perhaps been 4-5 sheets one on top of the other, and that the heat, having acted more strongly against the two or three in the middle, than against the first and the last, because they were less exposed to the wind, had almost entirely melted the pellets that composed them, and had formed these columns.

I often saw 2 stars of unequal size joined together. I observed the rays of the larger one were always longer and sharper than those of the other.

I judged that this was because the heat was stronger around the smaller star than around the other.

THis heat had more melted and blunted the tips of these rays: or else that this smaller one could also have been composed of a smaller ice pellet.

Double stars with 12 rays fell afterwards.

I judged that each one had been composed of 2 simple ones with 6 rays, by the heat which being stronger between the 2 sheets where they were than outside, had completely melted the small ice threads that joined them, and thus had glued them together.

As well as it had shortened those that joined the others, which I had seen fall immediately before. Now, among the several thousand of these little stars that I considered that day, although I took special care to do so, I never noticed any that had more or less than six rays, except for a very small number of these doubles that had twelve, and four or five others that had eight.

These were not exactly round, like all the others, but a little oval, and entirely as can be seen towards O. from which I judged that they had been formed at the junction of the ends of two sheets, which the wind had pushed against each other at the same time as the heat converted their small pellets into stars. for they had exactly the figure that this must cause.

This junction, being made according to a straight line, cannot be prevented as much by the rippling caused by the winds as that of the particles of the same sheet: besides, the heat can also be greater between the edges of these sheets, when they approach each other, than in other places, and this heat having half melted the ice particles that are there, the cold which succeeds it at the moment when they begin to touch can easily glue them together.

For the rest, in addition to the stars of which I have spoken so far which were transparent, there fell an infinity of others that day which were all white like sugar, and some of which had about the same shape as the transparent ones, but most had their rays sharper and more slender, and often divided, sometimes into three branches, of which the two on the sides were folded outwards on either side, and that of the middle remained straight, so that they represented a fleur-de-lis, as can be seen towards R; and sometimes in several, which represented feathers, or fern leaves, or the like.

With these stars fell several other ice particles in the form of filaments, without any other determined shape.

The whiteness of these stars is from the fact that the heat had not penetrated to the bottom of their matter.

This was evident from the transparent ones being very thin.

If sometimes the rays of the white ones were not less short and blunt than those of the transparent ones, it was not that they had melted as much in the heat, but that they had been more pressed by the winds: and commonly they were longer and sharper, because they had melted less; And when these rays were divided into several branches, it was because the heat had abandoned the small hairs that composed them, as soon as they had begun to approach each other to assemble.

When they were only divided into three branches, it was because the heat had abandoned them a little later; And the two branches on the sides folded back on either side outwards when this heat withdrew, because the proximity of the middle branch immediately made them colder and less flexible on its side, which formed each ray into a fleur-de-lis. And the ice particles that had no determined shape assured me that not all clouds were composed of small knots or pellets, but that there were also some that were made only of confusedly intertwined filaments.

For the cause that made these stars descend, the violence of the wind which continued all that day made it very clear to me, for I judged that it could easily disarrange and break the leaves that they composed, after having made them; and that as soon as they were thus disarranged, leaning one of their sides towards the earth, they could easily split the air, because they were all flat, and were found to be heavy enough to descend.

But if sometimes these stars fall in calm weather, it is because the air below, tightening, attracts the whole cloud to it, or because the air above, expanding, pushes it down, and by the same means disarranges them. whence it comes that for then they are usually followed by more snow. which did not happen that day.

The next morning snowflakes fell, which seemed to be composed of an infinite number of very small stars joined together: however, on looking closer I found that those inside were not as regularly formed as those above, and that they could easily come from the dissolution of a cloud similar to that which has been marked G above.

See the figure on page 214.

Then this snow having ceased, a sudden wind in the form of a storm caused some very long and fine white hail to fall, each grain of which had the shape of a sugar loaf. And the air becoming clear and serene just as quickly, I judged that this hail had formed from the highest part of the clouds, from which the snow was very subtle and composed of very delicate filaments, in the way that I have just described.

Finally, three days later, seeing snow fall all composed of small knots or pellets surrounded by a large number of intertwined hairs and which had no star shape, I was confirmed in the belief of everything I had imagined about this matter.