more extensive alternations, a large body or series of strata, consisting principally of Gneiss, often contains a number of alternating strata of other rocks in much inferior proportion. The dimensions of the strata of Gneiss are extremely various. They are generally very considerable where they do not alternate with the other strata already mentioned. Although Gneiss is a stratified rock, the several varieties of which it consists, present that disposition in very different degrees. When the texture is coarsely granular, and resembling that of Granite, the strata are generally least defined; and in some such, particularly when it abounds in Granite veins, it is difficult for an inexperienced eye to distinguish it from an irregular Granite mass. The same difficulty sometimes occurs where it is in very irregular position; either from a discordant inclination of the approximate portions, or from flexures and contortions. The difficulty is in this case increased by the circumstance, that such irregularities prevail most where Granite veins are most abundant: and such is the confusion hence generated, that it often requires an eye of no small experience to distinguish between the vein and the including mass; or to determine what is Granite and what is Gneiss. The distinction as already mentioned, in treating of Granite, consists in the general parallelism of the Mica or of the Hornblende, or else of some other ingredients. In composition, Gneiss fundamentally resembles Granite; as the prevailing minerals which enter into it are Quartz, Felspar, Mica, and Hornblende. To describe the mode in which these are combined, would be merely to repeat what has already been said of Granite. As in Granite, many minerals are found imbedded in Gneiss, in greater or less abundance. The colours of Gneiss vary from the same causes which influence those of Granite; and to repeat them would be superfluous. It may only be added, that the peculiar structure of this rock, by frequently causing the several colours to be disposed in stripes, produces a much greater

diversity of aspect in a series of specimens, than can be found in a collection of Granites."

In Fig. 4, we have a specimen of Gneiss, in which are distinct stripes of Mica. Fig. 5, one in which the various substances of which it is composed, lie in irregular streaks.

SERIES OF FAMILIAR CONVERSATIONS ON THE ANIMAL KINGDOM.

CONVERSATION VII.

CLASS ARTICULATA-SUB-CLASS INSECTS.

ORDER 1. Coleoptera, consisting of Beetles.

PAPA.-If you young folks have half an hour to spare this afternoon, and are disposed to spend it in my study,

I have a thought of opening my cabinet of Insects for your amusement.

HENRY.-That will be a high treat indeed.

ANNA.-O, yes, papa; there is nothing I so much wish for.

PAPA.-Well then, follow me into the study.

ANNA. How very nicely they are arranged. I suppose it is according to their order.

HENRY.—I am not a sufficiently good entomologist, father, to know on what the classification is founded.

PAPA.-Different naturalists have entertained very distinct opinions as to the principles on which the classification of insects ought to depend: but that of Linnæus, who founds it on the variety observable in the texture and number of the wings, is now most generally adopted. As you are a Greek scholar, you will at once perceive, by the termination ptera, that this cabinet is arranged on his plan. All these insects have attained the last or imago state; and I hope, with the aid of the microscope, that I shall be able to point out several interesting particulars respecting them.

ANNA. I do not quite understand what the word imago means, papa.

PAPA. It is a term, my dear, applied by Linnæus to the insect when it had reached its perfect state; because, having laid aside its mask, and cast off its swaddling bands, it is now become a true representative or image of its species. You observe that the bodies of all perfect insects consist of three parts: the head, the thorax or breast, and the abdomen. These parts are generally so attached by slender ligaments or hollow threads, that they appear divided.

HENRY. Is it not from this apparent division, that the appellation of insect is derived.

PAPA. Yes it is from the Latin, insecor, to be cut in, or notched. All insects, however, as you may at once perceive by casting your eye over this collection, are not alike in this respect.

HENRY.-No: the divisions are very visible in the wasp; but they are scarcely perceptible in the beetle. PAPA. The thorax or breast, which is this middle part to which the legs are joined, consists of three segments or divisions: to each segment one pair of legs is attached; and on the uppermost, you observe, the wings are placed. The abdomen is composed of annular joints or rings, differing in number in different insects: in some there are seven, in others, nine or ten.

HENRY.-Does the perfect insect breathe in the same manner as the larva?

PAPA.-Yes: insects, in all their states, breathe through small apertures, or spiracles, as they are termed; which are disposed along each side of the abdomen. Put this wasp into the microscope and you will readily see them. They are visible as small knobs of a roundish form, slightly elevated and perforated in the middle. These spiracles are also considered, with much probability, to be the organs of smell. As it is best, in whatever we do, to observe an orderly plan, I shall first point out to you the particular forms and adaptations of the limbs of the different little animals of this class; and I think you will agree with me, that small, and often invisible as they are, they display, in a striking manner, the wisdom and contrivance employed in their formation. We will begin with the legs; you observe that, as I said before, they are attached in pairs to the three divisions of the breast.

HENRY.-I suppose no insect has more than six legs?

PAPA. A few of the aptera genus, or those without wings, have the centipede, for instance, has at least four times that number: but in all that are furnished with wings, six legs, and only six, are invariably found. Each leg is divided into five parts: the coxa, or haunch; the femur, or thigh; the tibia, or shank; the tarsus, or foot; and the unguis, or claw:-but they are, as you may see, extremely different in their size

and form; indeed, from their various conformations, it is easy to recognise, even in the dead insect, the mode of life which the species is destined by nature to pursue. In the leapers, you see, such as the grasshoppers and some of the weevils, the thighs are remarkably thick and muscular; and the shank long and commonly arched-in those accustomed to dig in the earth, such as beetles and chafers, the legs are broad and sharp, often dentated at the edge:-in swimmers, they are long, flat, and fringed at the edge with hair-while in those that are intended to traverse our meadows, such as crane-flies, or long-legs, as they are vulgarly called, which you may observe by thousands on a summer's evening, readily making their way over the high grass, they are so disproportionately long and slender, that the little creatures seem to walk upon stilts.

HENRY. And the motions of insects are as various as the forms of their limbs.

PAPA.-Yes. As Cuvier remarks, they exhibit those of every other description of animals: they walk, run, and jump, with the quadrupeds; they fly with the birds; they glide with the serpents, and they swim with the fish. Indeed, whenever you go abroad in summer, wherever you turn your eyes, you may notice the variety of their movements. "They are flying or sailing every where in the air; dancing in the sun or in the shade; creeping slowly, or marching soberly, or running swiftly, or jumping on the ground; traversing your path in all directions; coursing over the surface of the waters, or swimming at every depth beneath; emerging from a subterranean cavern, or going into one; climbing up the trees, or descending from them; glancing from flower to flower; now alighting upon the earth and waters, and now leaving them to follow their various instincts."

ANNA.—I have observed that insects vary much in their paces too.

PAPA. They do. Some crawl along; others walk slowly; and others move with a very quick step. Num