frost would be dried up, and life upon it ren- | the experiments of the philosophers to remind dered impossible. Suppose that water as it froze contracted, instead of expanding, each stratum as it became congealed would descend to the bottom of sea, river, and spring, until the whole was converted into a mass as fixed in solidity as the mountains of granite. Water at 39° is contracted within the smallest space of which it is capable, and a quartmeasure contains more of it at that than any other temperature. This contraction at 39° Fahrenheit accounts for the fact that the water at the bottom of deep lakes is always found at this degree. During the nights of autumn the strata of surface water of the lakes are cooled; and as they become denser sink, while the warmer from below rise to take their place; and when in their turn reduced in temperature, also fall. us of the expansive power of freezing water. We hardly get through one of our severe winters without the bursting of a water-pipe to refresh our memory in regard to this scientific fact. It is surprising that the application of another scientific fact is not oftener made as a remedy for these inconvenient and expensive eruptions of freezing Croton. All pipes, however exposed to frost, may be kept secure by inclosing them in tubes of tin-plate, by which a layer of non-conducting air would always surround them, so as to prevent the water from reaching a dangerous lowness of temperature. Housekeepers can console themselves for their frequent domestic catastrophes during winter, Thus, when they persist in exposing their pitchers, and other vessels of feeble crockery, filled The water at 39°, at which it contracts with Croton to the hard frost of the night, they the most, and therefore acquires its greater will be able next morning, while picking up the density, must sink below all the rest. In the broken fragments, to reflect with philosophic summer the surface water of the lake becomes delight upon the scientific truth that water, heated, but being at the same time expanded when cold enough, will expand and break whatand, rendered lighter, it keeps its place. In ever resists its natural inclination for space. colder weather the surface and the rest may When the cold is excessive the strongest vessel, reach the same temperature-39°-when there though open, may be burst by the freezing of will be, of course, no change in position. In the liquid it contains, for the surface congealing winter the superficial stratum is turned into ice, first acts as a firm cover or stopper, and, resistwhich expanding and being consequently light-ing the subsequent expansion of the depths, the er, keeps above, and does not affect the depths below. The crust thus formed keeps the water beneath from cooling in cold weather; and in hot, although the surface is much warmed, the liquid conduction is so slight that the depths of the lake do not acquire any calculable degree of increased temperature. Heat is thus constantly stored up at the bottom of deep rivers, lakes, and seas, and the life of delicate animals and vegetables made possible even within the ribs of eternal ice. The resolute will of Nature is nowhere more manifest than in the exercise of this expansion of substances. Whether it be the conversion of a solid into a fluid, or a fluid into a vapor, the change is effected with an almost irresistible force. Water becoming steam, with its familiar might, hardly shows greater power than when turning into a solid. Take a cast-iron tube, fill it with water, and after closing its aperture with a stopper of metal screwed fast, expose it to the frost of a severe winter day. The result will be that the tube will be split, with a great noise like that of a cannon, from end to end, by the water trying to find space enough to expand into ice. An English officer of artillery at Quebec filled a bomb-shell fourteen inches in diameter with water, and after driving firmly into its nozzle an iron pin, threw it out where it was exposed to a severe Canadian frost. The stopper was soon forced out to a distance of more than a hundred yards, and cylinder of ice eight or nine inches long projected from the orifice. On repeating the experiment the iron pin kept its place, but the shell itself was rent in twain, and the crack filled with protruding ice. In this latitude we have no occasion for VOL. XXXVIII.-No. 227.-42 bottom is forced to give way. The mere moisture absorbed by the earth swells occasionally with sufficient force, when the cold is excessive, to overturn the most solid structures, and great rocks have been riven by drops of water frozen as they trickled through their crevices, and trees split by the sap arrested in its circulation and expanded to a solid by a sudden frost. During winter in our latitude it may be said without much exaggeration that it snows on every cold day even when the sky is cloudless. With a temperature sufficiently low the moisture which the atmosphere always contains freezes and forms small crystals of ice, so minute and transparent as not to be seen with the naked eye, but of such excessive sharpness as to be distinctly felt on every frosty day piercing the skin as the wind drives them against the exposed face. When the atmosphere is unusually moist these little crystals condense the watery vapor on their cold surfaces, and becoming thus enlarged grow into what we call flakes of snow. These, retaining the original crystalline form of their nuclei, possess the most beautiful shapes. Many hundred different ones have been counted, but all were merely modifications of a star with six rays. Water in freezing also assumes these graceful forms, but in the mass of ice the crystals are so joined together as not to be distinctly perceptible. By an ingenious contrivance the frozen casket may be made to disclose its hidden beauties. The glaciers which fill great mountain gorges and extensive valleys with Niagaras of ice, and sweeping down in their irresistible course tear away mountain-sides and crush every obstacle, leaving no trace of man and the puny structures he has audaciously raised under their threaten- | panded by the solar warmth into vapor, which, ing brows, are merely made of feathery flakes rising to the cold mountain heights, condense of snow which a breath could melt. On the into clouds and snow. tops of high mountains the watery vapor of the The geologists, as is known even to the most atmosphere is condensed in the form of snow, superficial student of the earth's history, attribwhich covers eternally their summits. "Some- ute much of the present condition of its surface times," says the French savant Cazin, "the to the effect of glaciers during what is termed masses of snow descend the declivities as ava- "the Glacial Epoch." The scientific traveler lanches, with a noise as of thunder, and fill the observes, almost every where he directs his valleys; sometimes they slip along slowly and skilled eye, the traces of these destructive accumulate at the base of the declivities in com- monsters of matter. In Switzerland, however, pressed masses. The air imprisoned in the where they are of a fresher date, though long flakes of snow is little by little expelled, and before the creation of man, he may see them the mass becomes still more solid; it presses more distinctly. Here he notices the rocky heavily on the rocks at the bottom of the higher borders of the valleys scored by deep furrows, valleys, and descends gradually toward the some of which are polished and rounded off, lower. Here, in consequence of the increased and others streaked or channeled, but all eviwarmth, it again attains the temperature of the dently produced by some down-tending mass freezing-point, and begins to melt. Then re- of irregular edges and gritty hardness, grindgelation takes place at an immense scale, be-ing, chiseling out, and rubbing on the stony cause the bottom of the valley and the sides of surfaces along which it has been impelled with the mountain present an obstacle to the gliding more or less speed. On the chalky slopes of of the ice. Continually impelled by its weight, the Jura, moreover, there are blocks of the the mass may break in overcoming the obsta- same granite which forms the summits of the cles to its progress, and immense and deep Alps, from which they must have been torn transverse crevasses result from the rupture. away and borne down by glaciers, until arrestSoon, however, the downward pressure of the ed at the places where they now rise as rugged consolidated snow and ice causes the sides of monuments of chaos. Similar operations are the crevasse to meet, and re-gelation takes place. now going on. Glaciers, as they descend the In the mean time other crevasses are produced slopes of the mountain, tear away and carry by the same causes, and the downward pressure with them great fragments of rock, which are continuing, are again compactly closed by the deposited here and there on their course, as the law of re-gelation. Thus the glacier moves slow-ice which holds them melts away. ly down the valley, at a rate of progress varying from fifteen inches daily in the winter to thirty inches in the summer, dragging here and there the debris of rock which have yielded to its efforts." Once in a warmer region, the great glacier melts without and within, and flows forth as a river, the source of which may be thus traced to a flake of snow. Tyndall has the credit of supplying, by an ingenious suggestion, a plausible explanation of the glacial epoch. He says that to account for its phenomena we have only to suppose, in that geological age, a more powerful condensing apparatus than exists at present. For this all that would be required would be loftier mountains, the summits of which we know increase in cold with their height. This being conceded, it might be possible, as is probable, that the temperature of the earth was much higher, even in the glacial period, than it is now. The sun may have distilled, by its greater heat, more abundantly and rapidly the seas into vapor, which, in its turn, having mountains with loftier summits to rise to, and therefore of greater cold, may have been condensed into more copious snows, and solidified into vaster glaciers. Those countries, therefore, where the " glacial epoch" has left its records, may be considered to have sunk, in consequence of the gradual depression of the surface of the earth, from the cooling and shrinking of its molten interior. The mountains of Switzerland have been unquestionably higher than they are, and traces of the sinking of the whole country are marked distinctly on the sides of the Alps and the Jura. This re-gelation-or freezing again-to which the formation of these great masses of ice is mainly due, is a process which is repeated by every boy who makes a snow-ball. The flakes of snow, by the pressure and warmth of his hand, are brought together and melted, so that they have the position, the freedom from air, and degree of cold necessary for union. With continued handling the snow-ball becomes, as we all know and are made to feel if struck by it, a hard mass of ice. Tyndall, the successor of Faraday, has shown such is the plastic nature of ice, that by forcing it in wooden moulds it may be made to take the form of lenses, spheres, cups, or even human and other figures. These simple experiments are all illustrated in the formation of glaciers, which are derived, as we have seen, from mere flakes of snow, which in turn owe their origin to the drops which compose the great bodies of water constituting so large a portion of our globe. The lakes, seas, All are familiar with the fact that ice is cold; and oceans, together with the mountains, form but many will be surprised to hear that when a vast distilling apparatus of which the sun is melting into water it is colder still. This is, the source of heat. The surface of these great however, a truth which scientific experiment reservoirs of water are being constantly ex-establishes and daily experience illustrates. The confectioner is not satisfied with pounding | keeping up a brisk current of air with the nozthe ice, but mixes salt with it before heaping zle of a pair of bellows thrust into the vessel. it about the vessel which contains the cream he This will rapidly change the liquid into a gas, desires to freeze. He, when asked why he by which sufficient cold will at once be promakes such a mixture, will simply say that it duced to freeze water. is for the sake of producing a greater cold; but how this effect results he will probably not be able to explain. The salt makes the ice colder merely by causing it to melt, and it causes it to melt in consequence of its avidity for water, which it can only obtain by turning the solid into a liquid. Such is the attraction of chloride of sodium (salt) for water, say the philosophers, that it overcomes the cohesion between the particles of ice. Substances are either solids, liquids, or gases, into each of which all may be respectively converted, according to the degrees of heat to which they are exposed. It is true that the natural philosopher and chemist have not yet been able to perfect their instruments so as to make ocular demonstration of the universality of the law; but the examples of obedience to it are so numerous as to leave no doubt of its existence. In all these changes of form, which are essentially due to heat, there are manifestations of its presence or absence-or rather of its increase or diminution, for it is never absolutely wanting. When a solid is turned into a liquid, and a liquid into a vapor or gas, cold is produced; and, with the reverse of these operations, heat is the result. In the first example, the heat is supposed to be consumed or exclusively employed in executing the change in the interior of the bodies, and therefore can give no outward sensible manifestation of itself; in the second, as the transformations are effected by what we term cold, or the absence of heat, there is no consumption or employment of this principle within, and it therefore exhibits itself without. So the melting of ice produces cold; and this is the purpose of what are termed freezing-mixtures, which are ordinarily made by mixing pounded ice and salt together. A considerable cold can, however, be produced without ice. Salt dissolved or melted in water will lower the temperature sufficiently to be indicated by the thermometer; and nitrate of ammonia, treated in the same way, will reduce it below the freezing-point. The mere diminution of the pressure upon moist air will, in consequence of its sudden expansion, produce a degree of cold quite manifest to the senses. Fogs, rain, and even snow are not seldom owing to this cause, and we can produce them artificially by this simple experiment. Take two glass reservoirs communicating with each other by stop-cocks. Put into one air saturated with moisture, and produce a vacuum in the other by means of the air-pump, and then open the communication between them, when a miniature storm will be the result, with its usual concomitants of wind, mist, rain, or snow. In tropical countries they use vessels of porous earthenware to keep their water fresh, which is the natural effect of the evaporation going on constantly from their surfaces kept in perpetual moisture by the transuding liquid. The cooling lotions of the surgeon owe their refreshing qualities to their ready evaporation. An old doctor says: "The frequent abuse of such applications will afford a striking illustration of the necessity of chemical knowledge for the preparation and direction of remedies. I have known a lotion of this kind applied to the head, when the patient has immediately covered it with a flannel cap, and thus converted into a rubefacient that which was intended to act as a refrigerant." An opposite mistake, and not less frequent one perhaps, is when spirits on being applied for the sake of creating a desired warmth are so exposed to the air as to evaporate and produce a dreaded cold. Any one who has been to sea must have noticed the old sailor, when asked the "way" of the wind, plunge his finger into his mouth and hold it up in the air before he ventures to deliver his unquestionable oracle. He seems, with his uplifted hand and solemn manner, as if engaged in some mysterious communion with old Boreas or some of his fellow-divinities of the elements; but his act is not one of superstition, but a philosophical process, though he might not confess to it under so dignified a title. The saliva on his finger evaporates most readily on the part exposed to the wind, and thus indicates by a greater cold its direction. Any one who in some way or other has got a good wetting and can not read mind the scientific fact that evaporation produces cold, and consequently avoid wind and all circumstances calculated to increase it. A dry over-coat thrown over his saturated suit will probably prevent all the evils of a chill. The one principle is apparent in all the various processes of producing artificial cold, which is universally the result of a change from a greater to a less density of form. The spirituous fluids, such as alcohol and ether, which evap-ily change his dripping clothes, should bear in orate readily and thus turn with facility from the liquid to the gaseous state, offer the aptest illustration of the effect of such a transformation upon temperature. A drop of sulphuric ether on the hand will produce by its quick change to vapor an immediate sensation of cold. A draft of air greatly facilitates the operation. Ice can be produced almost instantaneously by simply taking a thin glass tube containing water, and after putting it into a tumbler filled with cotton saturated with ether, The most intense cold ever produced is obtained by mixing frozen carbonic acid and ether together. By this a temperature as low as 212° Fahrenheit below freezing-point can be reached; and to the use of this artificial cold chemists are indebted for the solidification of certain sub To keep a thing cold in summer and warm in winter requires, curiously enough, although the results are so different, the same appliances. To preserve ice throughout the hottest weather we have to surround it, as we do ourselves in winter, with non-conductors. Thus the sides of our ice-houses are filled in with saw-dust or charcoal, and we wrap our crystal Rockland or Wenham Lake on the hottest day in August in flannel to keep it cool, as we in December envelop ourselves with the same material that we may retain our natural warmth. In the former case the non-conducting wool prevents the external heat from reaching what it covers, and in the latter it hinders the internal from escaping. stances which can not otherwise be made to | been raised by artificial heat. It is not safe, change their forms. By its touch flowing however, to rely too much on such means, for quicksilver is turned at once into a solid which these can only aid in keeping what we have, may be hammered, cut, or worked, as any other but not adding to our store; and this is essenmetal; but care must be taken not to grasp it tial, for the process by which heat is made is too firmly with the hand, for it will burn the necessary for other purposes in the human econflesh, or produce the same effect by the sudden omy equally essential to health. In cold weathabstraction of its heat as red-hot iron. If er, especially, we require a great deal of exercise moulds are filled with mercury, and surround- and a plentiful supply of pure air, that not only ed by the mixture of frozen carbonic acid and the human fire may be quickened, but that ether, busts and statuettes, glistening like silver, through the appetite thus increased we may be may be produced, and these will be frozen so constantly taking in fresh stocks of combustible hard that they will last for a considerable time. material. The most intense cold ever endured by man was 70° below zero, or 102° below freezingpoint, of Fahrenheit. Arctic travelers have been able not only to bear this excessive lowness of temperature, but while exposed to it to preserve their health and even enjoy life. Though their broth might thicken to a soapy solid during its short and hasty transit from the boiling pot on the fire to their hungry mouths, and their brandy become so congealed as to make it necessary to clip it into bits with a hatchet, and turn them well, like sugar-plums, under the warm tongue before they could be melted and easily swallowed, the temperature of their bodies would hardly vary. The easy adaptation of the human system to extreme changes from heat to cold and cold to heat is marvelous. Men have gone into ovens of a temperature of 212°, and, while beef-steaks were broiling and the kettle was sounding its steam alarum by their sides, have borne the excessive heat without much inconvenience and no subsequent suffering. Whether the surrounding cold be sufficient to solidify one's whisky, or the heat to cook his dinner, his own temperature must remain at about 98°. This is effected in the latter case by the abundant perspiration supplied by the natural water which forms so large a portion of the composition of the human body. This coming to the surface and being rapidly evaporated, and thus changing its form from a liquid to a gas, serves to keep down the temperature of the body to its naturally low degree. When exposed, on the contrary, to excessive cold, all the internal energy of the human system is concentrated in keeping up its internal combustion. This is aided by increased activity of breathing, the consumption of fatty and other substances which supply the animal fire with its carbon, or fuel, and the protection of the surface of the body with warm coverings. The object of dress in cold weather is not to give warmth, as many suppose, but to keep what the body may already possess. The heat we have is mostly of our own making, and is the result of the chemical action or human fire lighted within us; and we must take care, as we ordinarily do in winter, that its warmth shall not be used up too quickly for our natural means of keeping it going. These consist in enveloping ourselves in flannels, broadcloths, furs, and feathers, and when in repose living in an atmosphere the temperature of which has Nature, in its provident care, has freely dis tributed among its numerous dependents these non-conductors wherever they might prove the most useful. The eider-duck, a bird peculiar to cold climates, is furnished with a down which is almost impervious to heat. So with the swan and most birds, and especially their young, the plumage of which is exceptionally soft and light, as these fledgelings require more and produce less heat than those of stronger wing. This beneficent care of Nature has extended still further, and penetrated even to the egg, where the living principle has been warmly enveloped with a non-conducting albumen (white of the egg), and its vitality thus preserved in spite of its frequent deprivation by absence of the hen-bird of the maternal warmth. The eel, tench, and also the garden-slug, or snail, have the power of secreting a slimy fluid, which serves as a warm coat to protect them against exposure tô unusual cold. Those fish thus provided will live longer when drawn from their warmer element into the colder air than the mackerel, for example, which, having no such provision, is quick to die when landed. The blubber of the grampus and whale, as well as the corpulence of the alderman, are securities against freezing to death, although the former wallow in seas cooled by ice, and the latter waddle at the slowest pace exposed to the frost of a severe New York winter's day. Nature, by a wonderful process of compensation, is always equalizing its distribution of gifts, and thus cold and heat, practically as well as theoretically, become almost convertible terms, and life is made as enjoyable exposed to the freezing touch of the one as to the melting breath of the other. FALSE AND TRUE. Two walked under the olive-trees shading the walls of an ancient town, She whose youth he had sorely wronged, she whose heart he had starved and slain, Eating the bread of lonely toil she had waited through tedious years, Then with a languid, cold consent, after patience and hope were dead, Wedded another, whose constant passion sought her still, though her youth had fled. Moan of people and chant of priest rose and wailed like a soul in woe; Plumes like midnight and trailing sables slowly swept through the street below. "Oh, my darling!" she sobbed aloud, shaken sore by her utter woe; "Oh, my dearest, is this the coming which you promised so long ago? "Taunt me not with my broken troth, oh my love whom I still adore! You who lived in the love of women, winning, wasting for evermore"You who honor the empty husk of your vow when your lips are dumb, No proud woman has called you husband, and you come-as you pledged to come. "Loyal to him whose name I bore, yet I loved you, and only you; Judge between us, oh tender mother, which is the false and which the true!" |