exhaustion proceeds the mercury will fall, ecause there is a decreasing atmospheric pressure upon the surface of the metallic fluid, and when as much of the air as possible has been abstracted, nearly the whole of the mercury will fall into the cup. This experiment is quite conclusive, and demonstratively proves, that a fluid is sustained in an exhausted tube, because of the pressure which is exerted by the atmosphere upon its exposed surface. Soon after Perier had made his celebrated experiment, it was discovered that the height of a mercurial column varied in the same place, according to the condition of the atmosphere. This observation led to the use of the mercurial column as a barometer or weather gauge, for which purpose it is still employed. It can scarcely have failed to strike the mind of the reader, that as the fluid falls in proportion to the height above the surface of the earth, to which it is carried, it may be employed to measure altitudes. The importance of this application was appreciated, but at first considerable difficulties were experienced, and many errors were observed, for which the observers could not account. De Luc afterwards discovered that they, in a great measure, arose from not considering the different powers of expansion, possessed by mercury and air; for a temperature which would greatly expand air, might have no influence upon the volume of mercury. Many celebrated philosophers have been since employed in increasing the facility of measuring heights by the barometer, and so successful have they been, that a traveller may now always determine the relative altitudes of places by its means. OLD HUMPHREY ON OLD HOUSES. MOST people like to look at new houses, especially if they have any thing remarkable about them; now I like to look at an old one. As to a new house, whether it be of brick or stone, lofty or low, the builder himself does not know who will inhabit it Many a slip tween cup and lip," says the proverb; and many a man, who has a broad house built for him, lies in a very narrow one by the time it is completed. Yes! as to every new house, who shall say if it will be the mansion of joy or the habitation of sorrow? Who will venture to guess if its inhabitants will walk in the way that leadeth to eternal life, or hurry along the downward road to destruction? ! An old house is a text, nay, may prove a sermon to a reflecting old man, on the instability of earthly things. He regards the broken tiles, the tottering chimnies, the cracked window panes, the mouldering walls, and the shattered doors, hanging down on their rusty hinges; and, as his eye wanders over the desolate tenement, his thoughts turn to that crazy habitation, his own body, and he sighs as he passes on, In spite of patching and plastering, the old house must come down at last.' What a world of pains are taken to hide the ravages of time! An old house is often made to look like a new one, but it's an old house, my friends, after all. What if you do paint it with fresh paint, and point it with new-made mortar; will pointing and painting raise up the stooping walls, and strengthen the rotten timbers? No! no! your plans and contrivances will only answer for a time; do what you will, the old house must come down at last. I have heard of sad accidents occurring when the tenants of old houses have been careless in keeping them in repair, and especially when they have neglected to take warning by the bowing walls and decaying beams, that the building was about to come down altogether. Many have begun repairing too late, and some have been buried in the ruins of their own habitations. It is much the sameno! it is much worse, when, reckless of our lives, or regardless of our health, we needlessly run into danger, or live in an irregular manner, thereby injuring our health; but what fearful consequences follow when an aged and infirm person still calculates on a long life! When the hair turning grey, the furrowed brow, the loss of teeth, the dim eye, the weakly voice, and the faltering step, are all disregarded, till death, like a sweeping tempest, suddenly smites and shakes down the time-worn tenement. My aged friends, do you think of these things? You have had a long lease of it, but for all that the old house must come down at last. These crazy tenements of ours are but ticklish property, for though they are tenanted by immortal souls, there is no security for their enduring even an hour. We cannot make them proof against fire or water; nor insure them against plague, pestilence, or famine; battle, murder, or sudden death. How easy it is to talk of these things to others, and how hard to bring them home to ourselves. We speak well and act ill. We pass ourselves off for wise men, when we know that we are very fools. But whether we think or act wisely or weakly, time moves along, and takes us along with it. Every day I feel more and more that I am an old man, and that, though the time may be delayed a little longer, my remaining strength must pass away. Yes! yes! It is a sure and certain thing, that the old house must come down at last. When I rise in the morning, my cough at times troubles me sadly. My appetite is not quite what it once was. When I walk abroad, my gait is slower than it used to be, and if I drop my stick, I pick it up gently. When I sit down to read, I am fonder than I used to be of a large print, and my spectacles slide a little further down my nose. I love quietness better than bustle. At night, too, my chamber candlestick is taken up half an hour earlier than it was last year. In short, though I am blest, on the whole, with good health, and pass for a hale, hearty old man, I do feel, as I said before, getting older every day, and the truth oftener comes into my mind, "Have a care, Humphrey, for you have had many warnings; and so sure as you have had them, the old house will come down at last." Do not suppose, my old friends, that because I thus speak, I am over anxious for you to lose time in beautifying or repairing your weather-beaten habitations. It is not the tenement, but the tenant, that I wish you to be looking after; and if I begin by drawing your attention to the body, it is only that I may end by leading you to the preservation of the soul. Not that I purpose to weary you with my reflections. No! I wish to call forth your own, for one of your own reflections on this subject will be more useful to you than ten of mine. An hour's secret communion with your own heart will do you more good than listening to me for a whole day. I want to wind you up, and set you going, like a watch; and when I have done that, I may safely leave you to yourselves. Remember then that when the old house falls, the tenant has to look out for another habitation. Have you fixed upon yours? Is it built on the sands by the sea shore, or on a rock? When the floods rise, and the rains beat upon it, will it stand or fall? Is it a poor, perishing, earthly abode, that will soon pass away, or a building "not made with hands, eternal in the heavens ?" If you have thought of these things, you have acted wisely; and if you have not, think of them now; consult the wise Master Builder, and then, though the old house must come down at last, you will be received into new and everlasting habitations. INSECTS.-No. XXXI. [Magnified Blow Fly. Ditto, newly hatched.] Linnæus calls its imago state, because, AT length the insect reaches what having laid aside the mask, and cast off disguised or confined, or in any respect its swaddling bands, and being no longer imperfect, it is now a true representation or image of its species. This state is generally referred to, when an insect is spoken of without the restricting terms, larva or pupa. Singular as are the transformations of insects, we need not wonder that some of the metamorphoses described by the ancient poets were deemed possible. Utterly ignorant, as they were, of facts already stated, the change of a caterpillar into a butterfly would be likely to stagger an objector, who affirmed that they could not take place. Even Sir Theodore Margerne, the editor of Mouffet's work on insects, inferred, not two centuries ago, "that if animals are transmuted, so may metals." of the metempsychosis-transmigration The doctrine of souls from body to body-perhaps took its rise from the metamorphoses of insects. favour might be derived from the seemA plausible argument in its ing revivification of the dead chrysalis ; might be considered as owing to its reand its apparent reassumption of life ceiving for its tenant the soul of some criminal, doomed to animate an insect of similar habits with those which had defiled his human tenement. The Institutes of Menu drank wine, shall migrate into a moth or say, "A priest who has fly, feeding on ordure. the gold of a priest shall pass a thouHe who steals sand times into the bodies of spiders. If a man shall steal honey, he shall be born a great stinging gnat; if oil, an oil-drinking beetle; if salt, a cicada; if an household utensil, an ichneumon fly." Thanks be to God that we are not shrouded in such darkness; the gospel has brought life and immortality to light. At the present day, indeed, the transformations of insects, as they are called, have lost that excess of the marvellous which might once have furnished arguments for ancient dreams and fictions; and, wonderful as they are, they ought rather to be termed a series of developments. A caterpillar is not, in fact, a simple, but a compound animal, containing in it the germ of the future butterfly, inclosed in what will be the case of the pupa, which is itself included in the three or more skins, one over the other, that will successively cover the larva. As this increases in size, these points expand, present themselves, and are, in turn, thrown off, until at length the perfect insect, which had been concealed in the succession of masks, is displayed in its genuine form. That this is the satisfactory explanation of the phenomena, has been fully proved by several anatomists If, however, all this has in it nothing miraculous, it is still calculated to fill us with astonishment and admiration. Reason is indeed confounded at the thought, that a larva, at first no thicker than a thread, includes its own threefold, or sometimes eightfold coverings; the case of a chrysalis, and a butterfly, all curiously folded in each other, with an apparatus of vessels for breathing and digesting, of nerves for sensation, and of muscles for moving; and that these various forms of existence will undergo their successive evolutions, by the aid of a few leaves received into its stomach. And still less are we able to comprehend how this organ should at one time be capable of digesting leaves, at another only honey; how one while a silky fluid should be secreted, at another none; or how organs essential at one period to the existence of the insect, should at another be cast off, and the whole system which supported them vanish! Just after its exclusion, the insect is weak, soft, and languid; all its parts are covered with moisture, and, if winged, its wings bear so little the appearance, either in shape, size, or colour, which they are about to assume, that it might be taken for a creature only partially formed, rather than one in the most vigorous state of life. If it be a beetle, its elytra, or wing-cases, instead of covering the back of the abdomen, are folded over the breast; their substance is soft and leathery, and their white colour exhibits no traces of the several tints which are to adorn them. If the insect be a butterfly, or a moth, the wings, instead of being of their subsequent size, and variegated and painted with a variety of lines and markings, are, in large specie, scarcely bigger than the little finger nail, falling over the sides of the trunk, and of a dull muddy colour, in which no distinct characters can be traced. If the excluded insect is a bee, or a fly, its whole skin is white, and looks fleshy, and quite unlike the coloured hairy crust which it will become in an hour or two; and the wings, instead of being a thin, transparent, expanding film, are contracted into a thick, opaque, wrinkled mass. These symptoms of debility and imperfections, however, in most cases, speedily vanish. The insect, fixing itself on the spoils of the pupa, or some other convenient neighbouring support, first stretches out one organ and then another; the moisture of its skin evaporates, the texture becomes firm, the colours come forth in all their beauty, the hairs and scales assume their natural position; and the wings, expanding, extend often to five or six times their former size, exhibiting, as if by magic, either the thin transparent membranes of the bee or fly, the painted and scaly films of the butterfly or moth, or the coloured shells of the beetle. All this was witnessed with regard to a very interesting and beautiful butterfly, by an eminent naturalist, who says, " The pupa of this, being brought to me by a friend, I had the pleasure to see it leave its puparium. With great care I placed it on my arm, where it kept pacing about for the space of more than an hour; when all its parts appearing consolidated and developed, and the animal perfect in beauty, I secured it, though not without great reluctance, for my cabinet, it being the only living specimen of this fine fly I had ever seen. To observe how gradual, and yet how rapid, was the development of the parts and organs, and particularly of the wings, and the perfect coming forth of the colours and spots, as the sun gave vigour to it, was an interesting spec . tacle. It At first it was unable to elevate | sanctuaries, our refuge from misfortunes, or even move its wings, but their nume- our choice retreat from the world. rous congregations and folds gradually yielded, till they had gained their greatest extent, and the film between all the nervures became tense. The ocelli, and spots, and bars, which appeared at first as but germes or rudiments of what they were to be, grew with the growing wing, and shone forth at its complete expansion in full magnitude and beauty." To you, then, reader, it may be said, “ (Go, mortal, in thy reptile state, Enough to know to thee is given; Frail child of earth! high heir of heaven." But this thou canst only do, in its highest and noblest sense, through faith, which is in Christ Jesus. is not essential to the happy home, that there should be the luxury of the carpeted floor, the richly cushioned sofa, the soft shade of the astral lamp. These elegancies gild the apartments, but they reach not the heart. It is neatness, order, piety, and a cheerful heart, which makes home that sweet paradise it is so often found to be. There is joy as real, as heartfelt, by the cottage fire-side, as in the most splendid saloons of wealth and refinement. A CAUTION AGAINST PRESUMPTION, THERE is no encouragement for us to continue in sin, because of the falls of good men. If David falls, he must begin afresh, repent anew, cry, like a poor sinner who had never repented before, "Have mercy upon me, O God, according to thy loving-kindness; according unto the multitude of thy tender mercies, blot out my transgressions," Psalm li. 1. "Create in me a clean heart, O God, and renew a right spirit .Love of home is planted deep in the na within me," Psalm li. 10. If Peter falls, ture of man. The finger of God points to he is not to presume, "Oh, I have been home,and says to us all, There is the place to he must go cut and weep bitterly. If a believer, I cannot finally fall away :"find your earthly joy. Shall we appeal to Job falls, his former hearing, profession, the testimony of those who have sought joy elsewhere or have tried to find happi-begin again, he must learn to abhor himknowledge, are as nothing; he must LOVE OF HOME. ness in the world? We have but one an swer from them all-that the search has this world. What is the declaration of Byron, after having drained the cup of earthly pleasure to its dregs ? It is, That his life has been passed in wretchedness, and that he longs to rush into the thickest of the battle, that he may terminate his miserable existence by a sudden death. And Chesterfield, with rank, wealth, talent, polish, and power, after having stood, for half a century, the brightest luminary in all the European circles of elegance and fashion, has left his most decisive testimony of the heartlessness and emptiness of all those joys he had so eagerly pursued. As we go through this world of trial and of change, we can find our only joy in a life of faith in the Lord Jesus Christ, and domestic peace. Our fire-sides must be our self, and repent in dust and ashes. I urge this with earnestness. The doctrines of grace, which are the very glory of the gospel, must not be perverted into encouragements to licentiousness. Mistakes on this point are not uncommon. There are some who say to themselves, "Oh, I have heard of God, I know the plan of salvation, I have correct views of divine truth, I have heard the most eminent ministers; surely, I am not a babe in Christ: no need for me to be laying again the foundation of repentance from dead works." But if your knowledge and hearing, with your profession and attainments, have not kept you from returning to sin, you have need to repent, quite as much as, perhaps more than, that poor sinner, who, for the first time, is smiting upon his breast and crying, "God be merciful to me a sinner! JOHN DAVIS, 56, Paternoster Row, London Price td. each, or in Monthly Par ts, contain rig Five Numbers in a Cover, 3d. W. TYLER, Printer. 4. Ivy Lane, St. Paul's. THE PORCUPINE ANT-EATER. AMONG the many curious animals which the country of New Holland presents to the notice of the scientific, there are none more singular in appearance than the porcupine ant-eater, (echidna histrix.) In many of its anatomical details it closely approximates to the ornithorhynchus, of which we gave an account in No. 52 of this publication; it differs, however, in habits, manners, and external cha racters. The ornithorhynchus is aquatic in its habits, pursuing its food in lakes and sluggish sheets of water; on the contrary, the echidna is entirely terrestrial. It passes the greatest portion of its existence in deep burrows, which it constructs with great facility, being well provided with instruments for scooping or shovelling the earth. Its food consists of insects and their larvæ, together with worms, which it VOL. III. takes, like the great ant-eater, with its tongue. The external character of this remarkable creature may be thus detailed. The muzzle is elongated into a projecting narrow beak-like snout, cleft at the extremity by a small mouth, unfurnished with teeth. The nostrils are oval; the eye is small; from the base of this beak-like snout the forehead rises obliquely upwards, and is covered with bristly hair. The limbs are of enormous strength and thickness; the fore feet being divided into five hoof-like flat, blunt claws, reminding one of those of the chlamyphorus of South America ; the inner claw is the smallest. No better instrument could be devised for burrowing into the earth, or for tearing up the nests of ants, and other insects, on which the creature feeds. The hind feet consist also of five claws, of which the first is short, and rises like a thumb at the E |