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still.

Missolonghi is on the northern shore of the bay; to reach Patras, the steamer crosses to the Peloponnesus side, and here we leave the Ionian Sea.

There is now a railroad from Patras to Athens. On the morning when we made the transit there was given to us for our sole use a saloon on wheels, which was much larger than the compartments of an English railway carriage, and smaller than an American parlor car. In its centre was a long table, and a cushioned bench ran round its four sides; broad windows gave us a wide view of the landscape as we rolled (rather slowly) along. The track follows the gulf all the way, and we passed through miles of vineyards. But I did not think of currants here; they had been left behind at Zante. There is, indeed, only one thing to think

of, and the heart beats quickly as Parnassus lifts its head above the other snow-clad summits. We ought to have been crossing the gulf in a Phæacian boat, which needs no pilot, or, at the very least, in a bark with an azure prow. But even upon an iron track through utilitarian currant fields, the spell descends again when the second peak becomes visible at the eastern end of the bay.

"Not here, O Apollo,

Are haunts meet for thee,
But where Helicon breaks down
In cliff to the sea-"

How many times, in lands far from here, had I read these lines for their mere beauty, without hope of more! And now before my eyes was Helicon itself.

ICE AND ICE-MAKING.

BY T. MITCHELL PRUDDEN.

F one were to ask his friends what of-doors in winter when not kept fused

and most commonly used as food, the answers would probably be both varied and amusing. Salt would, I fancy, first suggest itself to many, and to those whose training in physiology and hygiene has not been neglected, no doubt the claims of lime and iron and carbon, which, in one form or another, we use with food to build up bone and brawn, would be amply urged. But, after all, it is water, for water is a mineral-a fused mineral. You will find it described as such, along with quartz and topaz and the diamond, in Dana's Mineralogy, or in other treatises on stones. We usually think of minerals as solid things, such as metals and rocks and jew els and various chemical salts. But when we consider the matter a little we see that all these things if melted by strong heat are minerals still, only they are now in a fluid instead of in a solid state. The difference between these minerals and water is that water gets fluid at a lower temperature than they do, and, like quicksilver, stays melted at ordinary living heat. But in those old ice ages which, one after another, have swept now over the Northern and now over the Southern hemisphere, bringing ruin and desolation, the natural and common condition of water was that of a solid-ice-as it largely is to-day out

or melted by the sun.

Everybody knows that water can exist as a solid (ice), as a liquid, and as a gas (steam).

The remarkable differences in appearance which water presents when in these different conditions depend simply upon the amount of heat which it contains. But what is heat?

Every well-informed person knows nowadays that heat is not a material thing as it was once supposed to be, which could be stored away in one substance and forced out of another, or which could be conjured into being here and annihilated there at the will of man. Heat is a kind of motion of the ultimate particles of which matter is composed. It is one of the ways in which what the physicists call energy manifests itself. Water, like all other substances, is made up of exceedingly small ultimate structures called molecules. And when these molecules of water are left to themselves, they tend to become grouped in certain definite ways to form a solid mass which we call ice. This is their natural resting state. When the molecules are exposed to the kind of motion or undulation which we call heat, they lose their fixed and definite relation to one another, and become mobile or vi

brant, and then we have the fluid-water. Increase this molecular motion by exposing them to further heat, and they shun one another in a frenzy of vibration, and this is steam. The curious thing about it is that the steam can only become water again, and the water ice, by giving up this heat to something else—that is, when the molecules can set a-swinging the molecules of some other thing.

If you put a lump of ice into a kettle of cold water and put it over a flame, the ice will gradually melt, but the temperature of the water will not rise above that of melting ice until all is fluid. A large amount of heat seems to have been lost. The force which this vanished heat represents seems to have been annihilated. It has not been lost, however, but has been simply transferred to the molecules which were still in the ice, but are now, in consequence of the heat transfer, swinging back and forth in the fluid water.

Heat the water still further, and the temperature will rise until it reaches the boiling point-100° centigrade or 212° Fahrenheit -and there it stays until the whole of the water has been converted into steam. Make the fire as furious as you like, not one degree hotter does the water get. The heat here too seems to be lost. It is not; but, as before, is converted into molecular motion a motion so intense that the molecules of the water fly apart, and thus make of the water a gas-steam. This heat, which disappears in melting the ice and in converting the water into steam, is called the latent heat of water and steam respectively, which means simply that it is being temporarily employed in inducing moderate or intense molecular motion.

Of

We are told, and can intellectually grasp the fact, that the heat which makes our earth inhabitable, and directly or indirectly supplies nearly all the varied forms of power which are used in the world's work, comes from the sun. the heat which is poured down upon the earth in the daytime a large portion is stored temporarily in the rocks and soil and water; much is used up in the evaporation of the water to form the atmospheric moisture and the clouds; much is consumed in the building up of the bodies of animals and plants. But all the time the supra-atmospheric spaces claim a large share of the stored-up heat.

readily communicated from one body to another by contact or by radiation.

We rarely realize, I think, how easily the earth parts with this heat, and how cold space is through which the earth sweeps in its orbit. Nor do we commonly appreciate how relentlessly space sucks away the heat which the earth has garnered from the sunbeams, out into its illimitable depths. 'Way out in space is a cold so intense that we fairly fail to grasp its meaning. Perhaps 300 or 400 degrees below the freezing-point of water, some philosophers think, are the dark recesses beyond our atmosphere. And night and day, summer and winter, this insatiate space is robbing us of our heat, and fighting with demoniac power to reduce our globe to its own bitter chill. So, after all, our summer and winter temperatures are only maintained by the residue of the sun's heat which we have been able to store up and keep hold of in spite of the pitiless demands of space. Our margin sometimes gets so reduced on nights in winter that we can readily believe the astronomers and physicists when they tell us that a reduction of the sun's heat by seven per cent. and a slight increase in the number of winter days would suffice to bring again to our hemisphere a new Age of Ice, with its inevitable desolation. The balance is really a nice one between the heat we daily gather from the sun and the share of it which we lose in space.

This is most comprehensible on cold winter nights. The genial sunbeams have struck the earth aslant, and but for a few hours, so that the soil and rocks and atmosphere have gathered during the day but little store to last over the long night; and from every exposed surface on the earth out rushes the garnered heat of the day into this more than freezing void. You can fairly feel it tugging at your face and hands.

Water out-of-doors in winter feels it too, and little by little grows colder and colder. The clashing of its molecules against each other, which is all that has made it a fluid, becomes less and less vigorous. Their mutual attractions, which have been antagonized and held in check by the furious commotion which the sun's heat had wrought, come slowly into play, until finally the molecules rush together in those groups and masses which we call crystals, and for the first time perhaps in Heat is of an unrestful nature, and is months or years sink into rest. The sym

phonies of motion in the water which the heat had conjured into being as it struck molecule upon molecule fade softly into a simple harmony of form at the bidding of insatiate space. A pellicle of crystal ice, once formed over the surface of

ICE STARS.

the water, transmits out into the cold space the heat from the water below, which so, film by film, grows stark.

Most fluids shrink as they lose their heat, but water, curiously enough, just as it becomes solid in freezing, expands about

of its volume, and thus becomes, bulk for bulk, lighter than water. And that is why ice forms a protecting cover to our streams and lakes and ponds; that is why icebergs swim so much above the surface instead of sinking in the sea; and that is why the mineral ice floats in the fused mineral, water, tinkling against the glass beside you as you dine. That, too, is why water-pipes burst in winter, and why those hoarse, uncanny boomings greet us in the night-time from freezing lakes and ponds.

We have seen that when water loses a certain amount of its heat it becomes solid. But something more than that occurs; it becomes crystallized. Ice is not like glass, simply a transparent solid, although to the eye it looks much the same. Certain substances, and among them water, when they pass from the liquid to the solid state, assume regular geometrical forms, and these are crystals. The diamond is crystallized carbon. Quartz is a crystallized compound of silicon and oxygen, just as ice is a crystallized compound of hydrogen and

oxygen.

The physicists explain crystallization by saying that the molecules of certain

substances possess mutual attractions, in virtue of which, when not held in abeyance by external forces, such as heat, they arrange themselves in fixed and definite relationship to one another. These relationships of the molecules are revealed in crystals by the geometrical forms which they assume.

Although these forms of crystals vary endlessly, they are all readily grouped in a very few simple systems. Some are simple cubes or modifications of this form; some are six-sided prisms, like the common rock-crystal, and like ice. The crys

tals may be very minute, or they may be very large; their sides may be broad or narrow; but the angles which their sides or faces form with one another are fixed and invariable. Crystals can grow, too, by the deposit of new material over the surfaces of the old.

When crystals or masses of crystallized minerals are broken apart, they tend to separate along certain definite planes, determined by the crystalline form, and called planes of cleavage.

Common rock-crystals or quartz crystals, such as spectacle lenses are some

&

ICE FLOWERS.

times made of, represent a crystalline group called, from their form, hexagonal prisms.

But we do not usually see the crystalline forms when we look at a lump of clear ice. It looks quite homogeneous and structureless, like glass, save that here and there bubbles of air may be

ROCK-CRYSTALS.

seen, which were caught and imprisoned when the water froze. The frost fronds on the window-panes in winter are frozen water, and although the crystals are very small and complex, they afford most readily seen examples of ice crystals.

The hoary coating seen on grass and twigs and fences on frosty autumn mornings, if looked at with a lens, will be found made up of tiny ice crystals, built out of the atmospheric moisture into forms so varied and fantastic as to defy description, and so delicate that at the lightest touch of an incautious breath they fade into dewdrops.

Snow-flakes are ice crystals formed of the frozen atmospheric moisture, and grouped in varied complex stellate forms of the rarest beauty. They may easily be observed when the snow is falling through still air if one catches them on a dark cloth, such as the coat sleeve. Varied and complex as are the forms which these six-rayed crystal snow-flake stars present, the angles which their rays form with one another are invariable, and if measured, will be found to be always sixty degrees, and every subsidiary ray makes precisely the same angle with the primary ray from which it shoots.

But what about solid ice? Where are the crystals here? Tyndall has shown us how we may reveal the crystalline structure of solid ice by passing a beam of sunlight through it. The heat which these beams carry with them into the solid ice liquefy it here and there in their track, and the liquid pools which are formed, if. examined with a lens, will be found to have stellate and branching forms similar to and not less beautiful than the snowflakes and the fronds upon the frosted window-pane. They are not indeed crystals, but "negatives" of the crystals flash

ing out at the dainty touch of the sunbeam in the forms in which they were laid together as the molecules of the water are released from their invisible bonds.

When ice commences to form out-ofdoors in winter, the first crystals shoot out horizontally over the surfaces of the water in delicate pointed spiculæ. These soon grow larger, and often stretch away in long, graceful, fernlike sweeps, or dart out from twigs and bits of grass in stellate masses. Finally coalescing at their sides as they advance, they form a roughened solid film covered all over in low relief with a bold and ever-varied tracery of most enchanting beauty. But now the direction of crystallization changes, and the water freezes directly downward, losing its surface markings as the sun now and then strikes and melts the top. Black ice at first it is-that is, ice so clear that it permits free vision into the depths where, as through a water-telescope, one stilly observant may see the water denizens at their work or play. But presently air bubbles are caught here and there through the ice mass, and it so becomes whiter and less transparent.

There is another curious and significant thing about the formation of crystals, and that is that the molecules, as they group themselves at the behest of their mysterious mutual attractions, are very intolerant of any foreign material which may be dissolved or suspended in the fluids out of which they are separating themselves in an order fixed as fate.

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This tendency is well marked and important in the freezing of water, for as the ice crystals slowly form and crowd so closely together as to make a structureless transparent mass, foreign substances, such as dust and sticks, or even smaller things than these, like the pigment particles which make ink black, or even materials wholly in solution, may be rejected by the forming crystals. Thus one may find clear ice formed on a mudpuddle, colorless ice spiculæ in an inkbottle, and comparatively fresh-water ice at the frozen borders of the sea. Even the air, which is held in invisible solution in considerable quantity in ordinary water, is forced out of it in bubbles as it crystallizes, and may be seen in streaks and layers in almost all natural ice.

On the top of natural ice blocks as they come to us in the market one usually sees a white layer, sometimes inconspicuous, sometimes occupying a considerable proportion of the thickness of the block. This is called snow ice, because it is usually formed by water soaking into the snow, which so often covers the ice in winter, and there freezing. This makes a solid mass, but it is thickly crowded with the little bubbles of air which were entangled among the snow-flakes as they lay together, and were caught by the water as it froze. These it is which make the so-called snow ice look white.

But aside from the snow layer on top, natural ice often presents layers or streaks of bubbles scattered through the block from top to bottom. These air bubbles are probably in part air which has risen from the bottom of the lake or pond or stream on which the ice was forming, and been caught beneath as the water was freezing downward. They are, however, largely bubbles of air which was in solution in the water, but which has been forced out by the purifying action of the act of freezing just described.

Ice which forms on some specially favored water may, however, be almost wholly without the snow covering, and almost bubbleless.

It is often interesting and sometimes profitable to stand apart a little from the rushing current of events, and trace the steps by which from time to time man has been led to hitch the forces of nature into new harnesses, and make them serve his needs and whims. The needs are often petty, the whims short-lived, as whims

are wont to be, and the end achieved, looked at as a spectacle, is often wofully devoid of impressiveness when set in fancy beside the grand results which Nature furnishes when she wields her forces untrammelled. These natural forces have lost their demoniac possession in these later years, and familiarity has bred indifference to if not contempt for those servants which do our bidding at the touch of a button, and change from lions to lambs at the twirling of a valve. But they still are faithful slaves in the service of the utilities.

The chief reasons which have led to the making of artificial ice in regions where the natural product can be gathered or be brought without too great expense are twofold-first, the desirability of having this important industry freed from the uncertain vicissitudes of the weather; second, the rapidly increasing pollution by sewage of many of the waters from which ice is cut for household use, and the growing conviction that serious disease may be incurred from the use of sewage-polluted ice.

The principle on which the manufacture of ice is based is exemplified in what has already been said about the relation of heat to the conversion of water into a gas-steam. A certain amount of heat is required for the conversion of any fluid into a gas. This heat becomes, as we say, latent-that is, is being employed for the time in producing violent undulations of the gas molecules.

Whenever a liquid is converted into a gas, heat must come from somewhere. In the making of steam, it comes from the fire; in the ordinary evaporation of water out-of-doors, it comes from the sun. When there is no special heating arrangement, but the conditions are favorable for the gaseous change in the fluid, heat will be taken up from surrounding substances if they have any. If you dip your hand in water, and then wave it through the air, the water will evaporate-that is, be converted into gas-and you will appreciate by the cool sensation that heat has been abstracted from your hand. If you use instead of water some fluid which more readily passes into the gaseous state, such as alcohol or ether, the sensation of coolness will be more immediate and intense.

Now this is the principle which is applied in the manufacture of ice. Some

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