life, "which groweth up like the grass, and to-morrow is cut down and withered." The swallows, like the flighty ambitions of our youth, or like false friends, have departed. For days before they leave us they may be seen assembling on church towers, elevated buildings, or willow plantations by the river sides. At first a few only perch, and, like touters for steam-packets, loudly scream that the company will start from that particular locality. Presently, high wheeling above our heads, we may see a thousand of their fellows, apparently in a high degree of excitement, screaming to each other as if they were determined to enjoy a good frolic before finally leaving the pleasant scene, and entering upon their long and dangerous journey. Gradually, towards sunset, we have seen them come down like a shower of birds, and blacken the point of rendezvous, where they rest till early morning, where we look for them in vain. Indeed, there appears something magical about their disappearance; for upon several occasions having observed their assemblage at nightfall, we have risen with the grey light of morning to see the host depart, but the travellers have always been up before the sun, and out of sight before we reached their rendezvous. It has been remarked "that no living creatures which enliven our landscape by their presence excite a stranger sympathy in the lovers of Nature than migratory birds. They interest the imagination by that peculiar instinct which is to them chart and compass, directing their flight over continents and oceans to that one small spot in the great world which Nature has prepared for their reception-which is pilot and captain, warning them away, calling them back, and conducting them in safety on their passage; that degree of mystery which yet hangs over their motions, notwithstanding the anxious perseverance with which naturalists have investigated the subject, and all the lively and beautiful associations of their cries and forms, and habits and resorts. When we think for a moment that the swallows, martins, and swifts which sport in our summer skies, and become cohabitants of our houses, will presently be dwelling in the heart of regions which we long in vain to know, and whither our travellers toil in vain to penetrate; that they will, anon, fix their nest to the Chinese pagoda, the Indian temple, or beneath the equator, to the palm-thatched eaves of the African hut; that the small birds which populate our summer hedges and fields will quickly spread themselves over the regions beyond the Pillars of Hercules, and the wilds of the Levant, of Greece, and Syria; that the thrush and the fieldfare, which share our winter, will pour out triumphant music in their native wastes, in the sudden summers of Scandinavia-we cannot avoid feeling how much of poetry is connected with these wanderers of the earth and the air." The swallows are a family of birds living upon insects, and in which the powers of flight attain their highest development, while the feet are comparatively useless for the purposes of locomotion. It occupies different positions in various classifications. The European species of this family are the "true swift," the "white-bellied swift," the "rock martin," the "rufous swallow," the "martin,” and the “sand martin.” The true swift, the rufous swallow, the martin, and the sand martin visit Britain in the summer time; the rest rarely or never come to our shores. In the true swift the leg is thickly feathered almost to the claws, and all the four toes are directed forwards. It will be seen from this that the swift cannot perch upon a bough or take hold of anything: its foot is in the same predicament that our hands would be if the thumb were removed. This beautiful creature comes to this country early in May, and leaves us towards the end of August. It comes the latest and departs the soonest of its tribe. It is the largest of the swallows which visit us; but its weight is exceedingly small when compared with its extent of wing-the former being scarcely an ounce, the latter nearly eighteen inches. Owing to the peculiar conformation of the feet to which we have already alluded, and which are smaller than in any other of its own species, it walks upon the ground with diffiulty, and finds it almost impossible to rise, because its feet render it no assistance in springing, and its wings and tail are so long as to beat the earth, and thus become less an aid than an impediment. We remember, a few summers ago, that a swift having been caught in its nest, was placed upon a grass-plat, and found itself quite unable to escape. It was suspected that its wings had been injured, or that some violence had been done to it in its capture; but, upon examination, no such calamity ppeared to have befallen it; indeed, while the question was being discussed, the swift took flight from the hand with perfect ease, and like an arrow darted up into its natural element, the air. It was remarkable that the nest, which was within reach of the window, was not forsaken by the bird, even though the graceful aëronaut was repeatedly caught at night in its place of roost. The swift is more upon the wing than any other swallows, and its flight is more rapid; hence its name-"swift." As it wings its graceful course it seems to announce its joyousness by a screaming of peculiar shrillness. It rests by clinging against a wall, and breeds under the eaves of houses, in steeples, and other lofty buildings, where it constructs its nest of grasses and feathers, and lays two long white eggs. Its colour is a dark glossy black, the chin only having a white spot upon it. It was a popular superstition at one period that there was in India a bird which had no feet, lived upon celestial dew, floated perpetually on the air, and performed all its functions in that element. Referring to this, Mr. Pennant says, “The swift actually performs what has been disproved of the bird of Paradise; except the small time it takes in sleeping, and what it devotes to incubation, every other action is performed upon the wing." The materials of its nest it collects either as they are carried about by the winds, or picks them from the surface of the ground. Its food is undeniably the insects which fill the air. Its drink is taken in transient sips from the water's surface. These wonderful birds rise very early and retire to roost very late, remaining in incessant activity during the long summer days. A pair whose motions we observed some years ago were on the wing, on more than one occasion, from a little after four in the morning till nearly nine o'clock at night. Those residing in a particular neighbourhood seem to assemble like human families before bedtime, and shrilly wish each other "Good night" in the high air, and forthwith, with one accord, to come down to their nests. Great power of sight is, of course, indispensable, both to enable the bird to obtain its food and to insure its safety in its rapid flight; but this power is not always sufficient to guard it against accident. Mr. Yarrell relates that he saw a swift, " on eager wing," dash itself against a wall; it was picked up stunned, and died almost immediately in the hands of the observer. In its northward career its visits are not confined to England, but extend to the 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, 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. CHAPTER XI. NOVEMBER. "Hung o'er the farthest verge of heaven, the sun * * * 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, 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. If a 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 & 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 |