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whole of Europe. When it leaves us it goes to the northern shores of Africa and similar latitudes. It has been seen at the Cape of Good Hope, and in the island of Madeira. The qualities of the swift are thus quaintly summed
up in the Portraits d' Oyseaux :
"Le Moutardier, ou bien grand Martinet,
Est à voler tres-leger et forte viste:
These birds, deriving their food, as they do, from matters floating in the atmosphere, are apt to catch at everything; and in the island of Zante the boys avail themselves of this circumstance to fish for swallows with a hook baited with a feather, and are related to have caught as many as five or six dozen per day.
Swifts and swallows are the inveterate persecutors of hawks; the latter are especially active in attacking such predacious intruders, and persevere as long as the opportunity remains.
In connection with this subject it will be appropriate to allude to the general structure of birds, and to point out the chief points in which they differ from other creatures. It is manifest that they must be very light, and yet, in the case of those who indulge in long flights, they must be very strong. Now it would appear that, to secure great strength, large muscles must be used; and these, to be efficient, must have strong bones to support them, as points of attachment. But the difficulty arises, how can this organization be combined with the lightness required? This, which might have puzzled any human architect, is achieved by the DESIGNER of the bird. All its bones are hollow, and can be filled with hot air each time the bird breathes; its body, also, is small in proportion to the extent of its wings. The covering of these denizens of the air presents every variety of texture and tint. How gorgeous is the metallic lustre of the peacock, the kingfisher, or the humming-bird! how rich the colours of the parrot or the flamingo!
"In plumage delicate and beautiful,
Thick, without burden, close as fishes' scales,
Or loose as full-blown poppies in the breeze,
With wings that might have had a soul within them,
Birds have no teeth, yet their food, in many cases, is of such a character as to demand mastication; but teeth would have been a very heavy piece of machinery. The food, when obtained, is transferred to the crop or craw, from thence to a membranous bag, where it is soaked in a kind of saliva, and then is conveyed to a third stomach, where the process of digestion is completed. In birds which feed upon grain, the sides of the stomach are of considerable thickness, and are surrounded by very powerful muscles. Here, with the aid of small stones and sand, the food is ground as in a mill, instead of being masticated by the teeth; yet comparatively few persons know that the gizzard, or stomach of the fowl, is such a curious piece of machinery. Our space here does not permit more to be said on this subject.
"Hung o'er the farthest verge of heaven, the sun
Through the thick air, as clothed in cloudy storm,
Then comes the Father of the tempest forth,
Wrapp'd in black glooms. First, joyless rains obscure
THE short dark days and the cold nights tell us that winter has come in the train of the yellow autumn. Plants and annuals alike seem dull, and many assume the aspect of death. Rattling hail or more penetrating sleet comes pelting pitilessly into the face of the poor pedestrian, or hisses down the chimney, where the fire, rendered necessary by the inclemency of the season, flickers before the family circle. Far away in the country, desolation seems to reign. The wind comes howling and mourning over the heath, or knocks the leafless boughs of the trees together with a dismal noise. Nature has changed her habit of joyful green for a robe of sombre russet, and the songsters-all save the cheerful robin-are dumb.
The fogs and mists of October and November are the terrestrial phenomena which are most noticeable in our climate, and which are a kind of reproach to us in the eyes of foreigners, living in latitudes where the temperature does not usually descend so low. The vapour of water, when completely taken up or dissolved in the air, is invisible; indeed, the atmosphere can hardly ever be said to be without a considerable quantity of water dissolved in it. At any time a glass containing a freezing mixture will be found to condense upon its sides the water which has hitherto existed unseen in the surrounding vapour. If you observe the cloud of steam from a locomotive, as it dashes on its iron way, you will perceive that the cloud at first is very thick, but that it gradually fades, till at last it "vanishes into thin air." The vapour of water, however, is only invisible when the
air is of as high a temperature as itself; for when the temperature of the air becomes lower than the point at which water can preserve its vaporous form, the latter becomes visible, and forms a mist or a fog.
Water, in the form of transparent steam or vapour, is continually rising into the atmosphere at all usual temperatures; even at, or below the freezing point, from ice and snow, evaporation goes on, for these solid substances gradually disappear without becoming liquid when the atmosphere is dry. Yet heat is the sole cause of the conversion of all liquids into vapour, and solids into liquids. Ice melts at the fireside, as also wax and tallow; the average temperature of the air is sufficiently hot to keep water in the fluid condition, but it is cold enough to freeze wax, tallow, lead, and iron.
The quantity of vapour given off by water is (other things being equal) in exact proportion, therefore, to the temperature of the atmosphere; and hence it is that the earth soon dries in summer, while the surface remains wet for a long while in winter. Just as hot water will dissolve more sugar than the same quantity of cold, so heated air will take up or absorb more water than cold air. Hence there is more water in the air in summer than in winter, and in hot than in cold climates. But some one may say, 66 "The weather is very damp in winter." This sense of damp arises from the fact that the vapour of water is in the act of condensation, or, in other words, that mist or rain is about to be formed on account of the coldness of the air.
So completely is evaporation regulated by temperature, that we find the quantity of vapour in the air diminishes in a regular proportion from the equator to the poles. This will appear at first sight contradictory, inasmuch as it asserts that the atmosphere contains more moisture over the great African desert of Zahara than over the fens of Lincolnshire. Any expansion of the air is accompanied with a readiness to absorb water. shallow saucer, containing water, be placed under the receiver of an airpump, and a part of the air removed, a considerable part of the fluid will rise under the glass, but will be quite invisible; but if the outer air be suddenly admitted, the internal air will be condensed, and the moisture which it had taken up will form a mist, and collect like dew upon the sides of the receiver. As the quantity of vapour which the air will contain at any time is limited by the state of expansion of the latter, and this expansion always depends upon heat under natural circumstances, we are only strengthened in our view, that the quantity of vapour of water in the air is regulated entirely by temperature. If the air be saturated with moisture, the abstraction of heat will make it contract and deposit some of the water as vapour, or cloud, or dew, or rain, in proportion as the reduction of temperature is great or little, gradual or sudden.
In so changeable a climate as ours there is a frequent tendency to destroy the transparency of the air, owing to the causes just named, and our atmosphere is rarely clear. But in early morning, soon after sunrise, if there has been a heavy dew (which means that the moisture of the air has been precipitated), before the sloping rays of the sun have had power to raise new vapours by evaporation, the air may often be discovered perfectly transparent even at this season of the year. On such occasions the view has a singularly beautiful appearance, owing to the sharpness of the outlines of the details of the landscape.
When the vapour has been accumulated in a great quantity in the air, and a sudden and considerable reduction of temperature takes place, a fog is
produced, which is, in fact, a cloud too heavy to float, and which rests upon the earth. The London fogs are proverbial; but in all large towns, especially those in which manufactures are carried on, there are similar phenomena. Their peculiarity consists in their being compounded of smoke and vapour, which gives them greater density than ordinary mists, and causes them to feel more unpleasant to breathe. At these times, if the observer walks a few miles beyond the houses, and gains the summit of a hill, he will find the sky clear and the air transparent; while in the housecrowded valley lies the fog, like an outspread garment, or a patch of snow, or a lake, with the spires and chimneys, and here and there the housetops peeping up through it above the level.
When the days become short, and the rays of the sun have very little time to warm the earth, the surface becomes very cold, and the air which is in contact with it deposits the moisture which it before contained; thus arises DEW:—
"Of bloom ethereal, the light-footed dews."
Dew is deposited, in the form of minute globules, whenever the ground is colder than the air; but upon these occasions the air does not lose its transparency. Sometimes the air contains so little moisture that although the earth becomes very cold, little or no dew is deposited. It is, moreover, rarely deposited in any considerable degree when the weather is windy or the sky is clouded. It is more plentiful in spring and autumn than in summer, probably owing to the greater difference in the temperature between the day and night in the two former, especially autumn. It is also more copious on those clear and calm nights which often occur early in November, and which are followed by misty or foggy mornings; or when a clear morning succeeds a night which was clouded in its first hours. When the clearness and stillness of the atmosphere are the same, more dew is formed between midnight and sunrise than between sunset and midnight. The cause of this is, evidently, that during the former part of the night the earth had not so completely given up its heat as it has during the hours after midnight. If, however, clouds hang in the sky, the heat which otherwise would be radiated away without any return, is reflected back again to the ground, and less dew is then to be found. This radiation of heat, and the production of cold thereby, are the subject of the following curious observations by Dr. Wells, which are not inappropriate here :
"I had often," he says, "in the pride of half-knowledge, smiled at the means frequently employed by gardeners to protect tender plants from cold, as it appeared to me impossible that a thin mat, or any such Himsy substance, could prevent them from attaining the temperature of the atmosphere, by which alone I thought them liable to be injured. But when I had learned that bodies on the surface of the earth became, during a still and serene night, colder than the atmosphere by radiating their heat to the heavens, I perceived immediately a just reason for the practice which I had before deemed useless."
Dew forms in very different quantities under the same circumstances upon different materialss-on metals sparingly, because they radiate heat imperfectly, but upon animal substances copiously, because they part with their heat more rapidly. And in conformity with the theory of radiation, it is observable, likewise, that whatever diminishes the view of the sky, as
seen from the exposed body, occasions a less deposit of dew bodies not so protected.
"The old tree hath an olden look;
The lonesome place is yet more dreary;
And summer paths are wet and weary."-MARY HOWITT.
BRIGHT, dazzling, frosty days, and glorious transparent nights, associated with crackling logs on the glowing hearths, are the ideas that cluster round the memories and experiences of December. Christmas holidays to the young, home reunions and merry meetings, seem almost essential to the realization of the time. It is called the depth of winter, and towards the latter part of the month the lowest temperature of the year is experienced. At the beginning of the month, indeed, there is sometimes mild weather, if the north or north-east winds do not prevail; and we remember in one instance recently to have seen a jasmine blossom, on a sunny aspect, as late as the 4th of this cold month.
The trees are bare, and all vegetation seems dead. When the first frosts set in, the effects of the cold upon growing vegetation are most singular. A plant which was green the day before is white with frost in the early morning which follows, and fades into a dismal black as soon as the sunbeams begin to warm the frozen branches, and melt the fringe of hoar-frost which sparkles upon the foliage which it killed while it adorned. The explanation is not difficult, for we find an analogy in the experiences of animal life. There are many animals which bear an exposure, for a considerable time, to severe cold, without suffering material injury; and these same creatures will often be able also to resist the injurious effects of an equal extreme of heat; but if they be suddenly removed from the cold to the heat, or the reverse, they suffer inflammation, mortification, and death. The human subject often, from severe cold, loses sensation in parts of the body; and these are precisely in a similar condition to the parts of plants under the influence of frost. The vital functions are suspended; the blood, like the fluid sap in the plant, ceases to flow; the nerves of sensation refuse to perform their office, either wholly or in part. If such a part of the body gradually passes from its dead condition no ill effects will ensue; but if an attempt be made, by the injudicious application of warmth, to promote a sudden reaction, the most serious results may follow. In slight cases chilblains will result; in severe instances of frost-bite, mortification and death. In Arctic regions the fingers, toes, ears, and noses are sometimes frozen; but the experience of the inhabitants of such regions has guided them to the true treatment of such injuries-viz., to rub the injured parts with frozen