tion of its combustibility, is rendered an invaluable article of fuel. If this be admitted to be the origin of coal, a satisfactory cause will appear for the vast abundance of vegetable matter with which the earth must have been stored in its early ages: this vast, and in any other view, useless creation, will thus be ascertained to have been a beneficial arrangement by Providence for man, the being of a creation of later date."

MAT. This is to me both new and curious. And I am thinking, that though one great convulsion, like that of the flood, might overwhelm the vegetable world, and lay it in one mass of ruin, something more is necessary to explain the number of beds, one above another, with other substances between, as you have described them.

MRS. L.-It is so-and a recent writer justly remarks, "How are we to account for such a surprising accumulation of vegetable matter, arranged in repeated Strata, sometimes to the number of sixty, and even more in a single district, separated from each other by intervening deposits of clay and sand? It seems certain that the Coral Strata were deposited within, and perhaps along the borders of great accumulations of water, whether fresh or salt: the Testacea (fossil shells) occurring in them, sufficiently prove this. Now the partial filling up of lakes and ponds, offers us the only analogies in the actual order of things, with which we can compare the deposits of Coal; for in such situations we often find a series of strata of peat, and sometimes submerged wood, alternating with others of sand, clay, and gravel, and presenting therefore the model of a Coalfield on a small scale and in an immature state. The devastations of successive seasons produce the repetition of these beds; and if we suppose a like order of causes to have operated more extensively and for a longer period during the formation of the Coal Strata, we shall find such an hypothesis is sufficiently in accordance with their general phænomena. To give you a

clearer idea of a Coal-field, I have drawn Fig. 3 a small section of one, and in Fig. 4 a representation of another curious fact respecting the Coal Fields, proving that they are not now as they were deposited: these are called Faults, and greatly disturbed the progress of the miner. They are thus described -

"The Faults, or as they may be most appropriately called, Dislocations of the coal-fields, are other and still more irresistible evidences of their having been affected by violent mechanical convulsions subsequently to their original formations. These consist of fissures traversing the Strata, extending often for several miles, and penetrating to a depth in very few instances ascertained; they are accompanied by a sinking of the Strata on one side of their line, or, which amounts to the same thing. an elevation of them on the other: so that it appears that the same force which has rent the rocks thus asunder, has caused one side of the fractured mass to rise, or the other to sink. Thus the same Strata are found at different levels on the opposite sides of these Faults, which appear to derive their name from their baffling for a time the pursuit of the miner; they are also called traps, and the elevation or depression of the Strata is described as their trap up or trap down, probably from a northern word signifying a step. The change of level thus occasioned by these dislocations sometimes exceeds 500 feet; whence we may infer the immense violence of the convulsion which had power to produce motions of such vast masses to such an extent. These fissures are usually filled up with Clay, which has since filtered in, and often includes fragments broken from the adjoining Strata: the creaks are usually vertical."

162

SERIES OF FAMILIAR CONVERSATIONS

ON THE ANIMAL KINGDOM.

CONVERSATION XIII.

CLASS ARTICULATA-SUB-CLASS ARACHNIDA.

ORDER 1-PULMONALIA, containing the Spiders, Scorpions, &c.

2-TRACHEALIA, Phalangium, or Shepherd's Spider-Mite.

ANNA. Do you see, papa, how busily this spider is weaving his net between the boughs of the jessamine tree? I have been watching him some time; for do you know, since our conversation on insects, I never see any without noticing them, and wishing to know their history. I think though you told me that spiders are not properly insects.

PAPA. No: they differ in several essential particulars from the insect tribes. Insects, you know, have no circulation of fluids-spiders have their heart and blood-vessels are very evident; and in consequence they have also organs that answer the purpose of lungs. In insects, the head is united to the body by means of slender threads-in spiders it is joined immediately to it. Spiders also in general have no antennæ, which you know form an essential part of the insect structure.

ANNA.-There are a great many different kinds of spiders, are there not?

PAPA. Yes, a great many-naturalists have enumerated upwards of fifty-each of which differs from the rest in appearance and manners. They are all alike, however, in being solitary and ferocious; and are to the insect tribes what wild beasts are to the flocks and herds. I believe they live entirely by prey. I have a good magnifying glass in my pocket, and while the spider is lying quietly, watching his net, we will examine him through it. You observe that, besides his large

web, he has made a small cell for himself, in which he lies in wait.

ANNA.-Ah! I see; it is just by, where he thinks he is out of sight, I suppose.

PAPA.-A spider is a very curious object in a microscope, but I fear we shall not see its different parts distinctly in this glass. It has eight eyes on the top of the head, which are variously placed in the different species. In some, they lie in two rows; in others, they form two sides of an angle; indeed they assume every imaginable difference of position. It is by the arrangement of the eyes, that the various species are distinguished.

ANNA. They seem to make good use of their eyes, I think; for I have observed that they perceive a thing in a moment, and they are very active.

PAPA.--Yes; they are capable of great activity; and all their movements imply great perfection of sight and hearing.

ANNA. What sort of a mouth has a spider, papa?

PAPA.-Its mouth is formed for sucking fluids, and I believe it lives chiefly on the juices of the insects it catches. Though it has no teeth, it has what answers its purpose as well. In the fore-part of the head, at the mouth, there are two fangs, or sharp crooked claws, which stand horizontally, and when not in use, are concealed in two cases contrived for their reception, in which they fold like a clasp knife. At the point of each claw, there is a small hole, which emits a kind of poison, and with these claws, they tear and kill their prey with great dexterity and dispatch.

ANNA. What cruel little creatures!

PAPA. You see the hinder part of the body is separated from the breast by a small thread-like tube.

ANNA. It looks as if it was quite divided. In that respect it is an insect, I suppose.

PAPA. Yes; it is like an insect in that particular.
ANNA. I think it has eight legs, has it not, papa?
PAPA. Yes; all the species of spiders have eight

legs, with three joints in each, terminating in three crooked claws. Do not you admire its beautiful skin, Anna? Look at it through the glass-it is, you see, a hard polished crust.

ANNA. It is indeed very beautiful. But what I most admire in spiders, is their skill in spinning and weaving.

PAPA.-It is a part of their history well deserving of your curious attention. The spider has four or six little tubercles or spinners at the hinder part of the body, each of which contains a multitude of tubes so numerous and so exquisitely fine, that a space, often not bigger than the point of a pin, is furnished, according to Reaumur, with a thousand of them. From each of these minute tubes, the spider spins a gluey thread of inconceivable tenuity; and the threads from all these tubes uniting together, form that which we see them use in making their webs.

ANNA. Then each spider's thread that is visible to us, is composed of four or six thousand others: astonishing!

PAPA.-Yes; even those of the smallest species, some of which, you know, are so fine as to be almost imperceptible, are in reality ropes composed of at least four thousand strands.

ANNA. And these complicated threads are not after all so thick as a hair.

PAPA. So thick as a hair! my dear-a thousand of them would scarce form one so thick as a hair of your head. When the spider (I speak of the garden-spider more particularly, because we have an example of one before us, begins to weave, she fixes the end of her threads by applying the spinners to any thing that happens to be convenient; and the threads lengthening in proportion as she recedes from it, she fixes them to something on the opposite side. In this way she forms the margin of her net, which she takes special care to render strong by gluing several threads together. The founda