culties, which has already been often brought under our notice, and which Addison describes as "an immediate impression from the First Mover, and the Divine energy acting in the creatures."

In describing a coral formation called Ducies Island, he informs us that it takes the shape of a truncated cone, with the base downward, which can be demonstrated to be the form best calculated to resist the action of the water; and he proceeds thus:-"The north-eastern and south-western extremities are furnished with points, which project under water, with less inclination than the sides of the island, and break the sea before it can reach the barrier to the little lagoon formed within it. It is singular, that these buttresses are opposed to the only two quarters whence their structure has to apprehend danger, that on the north-east, from the constant action of the trade-wind, and that on the other extremity, from the long rolling swell from the south-west, so prevalent in these latitudes; and it is worthy of observation, that this barrier, which has the most powerful enemy to oppose, is carried out much farther, and with less abruptness, than the other."

There is another circumstance, no less remarkable, mentioned by Amoureux, a natural historian, who has paid particular attention to the operations of the coral insect. "Some," says he, "by their union or aggregation, form a long narrow ridge or reef, which extends uninterruptedly several degrees, opposing an immoveable rampart to the great currents of the sea, which it often traverses, the solidity and magnitude of which increases daily. Sometimes this line of madrepore rocks assumes a circular form. The polipes that inhabit it gradually elevate their rocky dwelling to the surface of the sea; working then in a sheltered basin, they, by little and little, fill up its voids, taking the precaution, however, to leave in the upper part of this impenetrable wall, openings by which the water can enter and retire, so as to renew itself, and furnish them with a constant

supply of their aliment, and of the material with which they erect their habitation."

In reference to a Final Cause, the observations of these authors are exceedingly striking. Here is an animalcule, bound to a particular locality like a plant, and appearing scarcely to possess qualities superior to a vegetable, yet acting in concert with innumerable individuals of its species, not only to erect structures extending for hundreds of miles, but, in the mode of the combined operation, displaying an extent of scientific skill, which rivals the wisdom of the most experienced engineer, while the structures themselves incalculably exceed his power. When we observe such a society of animals not only erecting their buildings in the form best calculated to resist the force of the ocean, but even raising buttresses and breakwaters in the places most liable to be assailed, and proportioning them, with consummate art, to the force of the current they have to resist ; and when we further find them, with remarkable precaution and forethought, leaving openings, where necessary, for the entrance and reflux of the tide, so as to keep up, by a constant renovation of the waters, an accession of food and of materials for their work,-how is it possible to withhold an acknowledgment, that the instincts thus indicated are derived from an intelligence not their own?

But, if we look further, and consider the ultimate effect of these structures,—if we trace them gradually rising from the deep bed of the ocean, till they fill up vast tracts lately occupied by a waste of waters, and lay the foundation of future islands and continents, the habitation of living beings, we shall discover new grounds of surprise and adoration. That these scarcely animated polipes should be capable of effecting all this, and should, in truth, have already to a considerable extent effected it, affords a singular view of the operations of Providence, and seems to corroborate those anticipations which originate in other sources, respecting future changes in the history of the human race. From considerations

arising from the extraordinary vigour of reproduction in the animal world, and of the power of human industry and skill in increasing the supply of esculent vegetables, both by their selection and by the cultivation of the soil, I have shown the probability of a further rapid and most extensive multiplication of human beings, and of animals and vegetables fitted for their use; and, in the labours of the apparently insignificant coral animalcule, there seems to be still another means by which this beneficent end may be destined to be accomplished. It is true, that the progress of coral formations is slow; but the operation is on an immense scale, proceeding, in the warmer climates, in every region, and almost in every locality, where rock is to be found at the bottom of the ocean, at such depth as to be within the influence of the light. A few ordinary shocks of an earthquake might, according to Mr Lyell's observations, cause vast tracts of these already formed reefs and shoals quickly to emerge from the sea; and we know that, in this case, various provisions, elsewhere alluded to, are made by Providence, by which they would soon be covered with vegetation, and rendered habitable. We cannot, indeed, penetrate the future intentions of the Universal Governor; but we, at all events, behold, even in the lowest view we can take, a most wonderful and interesting manifestation of benevolent action. "To me," says Mr Ellis, after an elaborate investigation of the history of living corallines, "these disquisitions have opened up new scenes of wonder and astonishment, in contemplating how variously, how extensively, life is distributed through the universe of things; and it is possible that the facts here related, and these instances of Nature animated in a part hitherto unsuspected, may excite the like pleasing ideas in others; and, in minds more capable and penetrating, lead to further discoveries, further proofs (should such yet be wanting) that One infinitely wise, good, and allpowerful Being, has made, and still upholds, the whole of what is good and perfect."

FIFTH WEEK-SATURDAY.

INSECT TRANSFORMATIONS. THEIR COCOONS.-THE SILK

WORM.

THE transformations which terrestrial insects undergo in the course of their existence, have been frequently alluded to in the preceding volumes; and some of them have been described, in reference to their hybernation and reproduction. The subject, however, is at once copious and interesting; and as this is the season when many of these metamorphoses take place, I willingly recur to it.

The first process to which I shall advert, as connected, in many insects, with these transformations, is that by which they prepare for themselves a shroud of silk for their temporary retreat, during the insensible state into which they are thrown while undergoing their most important changes. It is interesting to observe the various ways in which similar contrivances are adapted by the Creator to the fulfilment of different purposes. The spider, as we have seen, spins and weaves nets to entrap her prey, she also spins cocoons for her eggs; while all the caterpillars of butterflies, of moths, and, in general, of insects with four wings, spin silk of various degrees of fineness and strength, for enveloping their bodies like mummies, while in the chrysalis state.

In order to understand the nature of the apparatus by which a caterpillar spins its silk, it is to be recollected, that its whole interior structure differs from that of warm-blooded animals. It has, properly speaking, no heart, though a long tubular vessel, which runs along the back, and beats from twenty to a hundred times in the minute, has been called so. It differs also from the higher orders of animals, in having no brain, the nerves

running along the body being only united by little knobs, or ganglions; and no lungs, their office being supplied by eighteen spiracles, situated along the sides. The spinning apparatus is placed near the mouth, and is connected with the silk bags, which are long, slender, floating vessels, containing a liquid gum. The bags are closed at their extremity, become wider toward the middle, and more slender toward the head, where they unite to form the spinning-tube or spinneret. The bags being in most cases longer than the body of the caterpillar, necessarily lie in a convoluted state, like the intestines of quadrupeds.

The following observations, by the Abbé de la Pluche, will explain the nature and use of the spinneret :"You may sometimes have seen, in the work-rooms of goldsmiths or gold-wire-drawers, certain iron plates, pierced with holes of different calibres, through which they draw gold and silver wire, in order to render it finer. The silk-worm has, under her mouth, such a kind of instrument, perforated with a pair of holes,* through which she draws two drops of the gum that fills her two bags. The instruments are like a pair of distaffs, for spinning the gum into a silken thread. She fixes the first drop of gum that issues, where she pleases, and then draws back her head, or lets herself fall, while the gum continuing to flow, is drawn out and lengthened into a double stream. Upon being exposed to the air, it immediately loses its fluidity, becomes dry, and acquires consistence and strength. She is never deceived in adjusting the dimensions of the apertures, or in calculating the proper thickness of the thread, but invariably makes the strength of it proportionable to the weight of her body."+

The silk-worm, to a description of which I intend at

These two holes Lyonnet has discovered, on minute inspection, to be united into one. He has also discovered, that the united tube has a power of contraction and expansion, by which the insect can make the silk coarser or finer at pleasure.

† Spectacle de la Nature, vol. i.