Bentley.wilson Snow.beauties

7/27/2019 Bentley.wilson Snow.beauties

1/4

"Snow Beauties" Wilson A. Bentley(1865-1931)

What magic is there in the rule of six that compels the snowflake to conformso rigidly to its laws? Here is a gem bestrewn realm of nature possessing thecharm of mystery, of the unknown, sure richly to reward the investigator. Forsomething over a quarter of a century I have been studying it and the workhas proved to be wonderfully fascinating, for each favorable snowfall, duringall these years has brought things that were new and beautiful to my hand. Ihave never yet found a time when I could entertain an idea of relinquishing it.During the time that I have carried on the work, I have secured sixteenhundred photo-micrographs of snow crystals alone, and no two are alike. Isthere room for enthusiasm here? Doubtless these pictures serve to representwith some fairness almost every type and variety of snow that occurs innature, but they show scarcely an infinitesimal fraction of the individualvariation of form and interior design among the countless myriads of crystalscomprising each type.

The clouds, and the tiny liquid particles - water dust- of which they consist,play no part in true snow crystal formation. They coalesce only to form theamorphous - granular - varieties of the snow, or to coat true, mature crystalswith granular material. The true crystals, forming the bulk of the snowfall, areformed directly from the almost infinitely small and invisible molecules of

Water in solution within the air, and floating between the vastly larger cloudparticles.

Most of the crystals are, of course, imperfect, made so especially during thickand heavy snowfalls, largely as a result of crowding and bunching duringdevelopment, or to fracturing due to violent winds. In general, the westernquadrants of wide spread storms furnish the majority of the more perfecttabular shapes. As a rule low clouds, if relatively warm, tend to produce themore rapidly growing open branching forms, and the inter mediate and upperclouds, if relatively much colder, the more solid, close columnar and tabular

forms. Sometimes, however, crystals differing but slightly or not at all fromthose falling from storm clouds, drop out of apparently cloud-free skies.

Much wonder has been excited, because the snow crystals exhibit such abewildering diversity and beauty. They form with in a very thin gaseoussolvent, the air, and this allows the molecules of water an unexampledfreedom of motion and adjustment while arranging themselves in crystal form.The fact doubtless largely explains why the crystals of snow far exceed othercrystals in complexity and symmetry. Snow crystals, like all crystals of water,develop under the hexagonal system and invariably divide into six. Nothing

absolutely certain is known as to why they grow thus, except as it is assumedthat the number and arrangement of the attractive and repellent poles


2/4

possessed by the molecules of water, impose this habit of growth upon them.This dividing into six is necessarily discussed and best explained in somewhattechnical sounding terms. We may assume each water particle or moleculepossesses two opposite primary poles, positive and negative, correspondingin direction with the main tabular axis of the crystals, and in addition three ofsix equidistant secondary poles arranged around what may be called theequatorial diameter of the molecules. Water, being a dia magnetic substance,and susceptible to polar repulsion, presumably has a tendency to arrangeitself thus, in a position between and at right angles to the primary electro-magnetic poles. This alignment of the lines of growth, opposite to the lines ofgreater magnetic force, would compel the crystals of snow to grow mainlyoutward in the directions of their equatorial diameters and secondary poles.This theory would perhaps best explain why the crystals grow upon thintabular or in the hollow columnar form, and increase so little in the direction oftheir main axes, that is, in the direction in which, it is assumed their mainpositive and negative poles lie.

Each of the six parts or segments of the crystals, while in process of growth,increases simultaneously outward, yet each one usually grows independentlyand by itself. So each of the six parts may, for all practical purposes, beconsidered as being a separate crystal by itself, and the whole as being anaggregate of growing crystals. And the law under which they form not onlygives them a general hexagonal plan of growth, but in addition gives them twospecific secondary habits of growth under the same plan.

We may best distinguish these as the outward or ray habit, and the concentricor layer habits of growth respectively. The ray habit causes growth to occuralways outward and away from the nucleus. This tends to produce openbranching forms. Crystals that grow rapidly, or within relatively warm lowclouds, usually build upon this plan. In the case of the concentric or layerhabit, growth tends to arrange itself in massive form, around the nucleus. Thistends to produce the close, solid flakes. Slowly growing crystals, as thecolumnar, form solid tabular hexagons, and all such as crystallize in a verycold atmosphere, or at great altitudes, usually grow according to this latterhabit. Snow producing clouds, if single, are perhaps as a rule of some depth,

or if double, or multiple, vary one with another in temperature. The growth,habits and conditions under which the crystals form therefore are commonlyunstable, with a multiplicity of diverse conditions, tending to hasten or to retardtheir rates of development, and momentarily, at least, to change or modifytheir forms. This state of things may cause them to grow after solid plans atone moment and altitude, after branching plans at another, after compositeplans at yet others, and tends to cause them to become increasingly complexin outline and structure as growth progresses.

In those especial cases where the crystals form and grow wholly within asingle relatively thin and uniform cloud, as within low detached clouds, for


3/4

instance, they are likely to follow from start to finish after one single, uniformplan, and all be very much like each other. The frail branching snow crystals,falling during snow flurries, are oftentimes of this character. In some cases,the crystals will form composite fashion, after but two specific plans. A solid,mosaic centerpiece portion will form within a cold upper air stratum and, fallingearthward, acquire branching additions at some lower, warmer level.Composite crystals of this character perhaps exceed all others in beauty ofdesign, combining into one, as they do, the two most beautiful types of snow.

It is all most marvelous and mysterious, these changing habits of growth, andthis momentary shifting about of the points of maximum development. Growthofttimes occurs in alternate order, first at the corners of the hexagon, and thenat the sides. In some cases, this pendulum-like swing of outgrowth maycontinue from beginning to end.

But perhaps the most wonderful fact of all is the marvelously symmetrical wayin which all this is accomplished. If a set of spangles or branches, or tinyhexagons or other adornments, form and grow at certain points upon any oneof the six, or alternate, rays, or segments, similar or identical ones are almostsure to form at the same places and moments on all of the others, so that thebalance of form is always kept unimpaired.

It appears as if the magic that does this might be, in part at least, of an electricnature, and due to the presence of tiny electric charges around their

peripheries. Would not the presence at certain points, and the absence atothers, of tiny electric charges, shifting momentarily about, as fresh chargescollected, and causing momentary realignments in the locations of the severalcharges, stimulate growth at certain points and retard it at others? It seemsworth while tentatively to advance this theory, as a possible explanation ofthese perplexing mysteries. But it is a fascinating mystery this, that thecrystals assume such a marvelous diversity of form, though forced by thecrystallographic law under which they come into being to assume always thehexagonal form. Six rays or parts, there always are, yet what an amazingvariety these parts exhibit among themselves. Individual crystals of the open,

branching variety, differ one from another, in the shape, size or thickness oftheir primary rays and these rays in turn, in the number, size or shape, of thesecondary branches that they possess. Those of solid tabular form differ as totheir layers, or segments, and in the number and arrangement of the air tubesand shadings within them. Similarly those of a quasi-open formation vary inindividual cases. In their spangles, the tiny hexagons composing them, as wellas in the way in which these are combined with each other, or with rays, andarranged around the central nucleus. Yet in innumerable cases the crystalsassume, at some one or more stages of growth, identical forms and outlines. Itoften happens that their nuclei, or ultimate outlines are alike, yet it seems to

be rarely the case that any two pass through a long series of such changes ofform. Hence the astonishing variety.


4/4

Documents

Bentley.wilson Snow.beauties