pressive effects of the volcano, that we arrive, in a measure, at an idea of those changes to which it is apparent the globe has been subject, and by which many parts of its surface, indeed whole countries, have been materially diversified. The contemplation of its phenomena has been, in the mind of the geologist, the avenue to the basis of a theory on the formation of rocky substances; and since its sublime concomitants are not limited to the production of ignited bodies, but, as before observed, occasionally cause a violent projection of water, so it in a considerable measure favours the hypotheses both of Hutton and Werner; the former of whom referred the deposition of many bodies to original igneous fusion, the latter, to previous aqueous solution. We may, therefore, consider, that it is still a matter of doubt which theory is to be embraced, and, on the whole, that there are many circumstances favourable to both.

In a former state of our planet, it is certain that volcanic fires were more extensively found, and more active in their operation. In proof of this, we find the remains of immense extinguished volcanoes, variously scattered; and, moreover, the products of their action, viz: volcanic rocks in almost every country hitherto explored. This interesting sub ject has been only recently particularly examined, and I shall commence with a description of the external features of these mountains. Many volcanoes are lofty mountains with a truncated cone, having an aperture at the summit nearly circular, and varying in depth, from which eruptions issue; sometimes, however, these happen at the foot of the mountain or at the side, and in others are even submarine.

The greatest number of burning mountains are situated near the sea or large lakes; and this circumstance favours the hypothesis of those who refer them to the agency of water. Most isolated volcanic mountains are of a conical or pyramidal form, in the centre of which cone the crater is situated. This cone ascends from the plain at the top of a gradually ascending mountain. The sides of this cone are covered with sand, ashes, pumice, &c. and its form, and the nature of its materials, prove its production from the earth below; which projecting the sconce, &c. in a perpendicular direction, they have fallen and accumulated in this way.

The form of the cone is changed during great eruptions, and generally more or less by one, though comparatively small. Thus a considerable part

of Vesuvius fell in in 1794, and 100 feet of its upper part in March 1828. In 1677, when M. D'Orville visited Vulcano, one of the Lipari isles, two distinct cones, each on a base, and each containing an active crater, existed. Now there is only one. The Abbé Spallanzani visited the mountain sixty years after, and, on enquiry, found that the oldest inhabitants recollected the double cone. The volcano, however, has not always a conical form; Humboldt observed much difference, both in form and relative situation, between the burning mountains of the old world and the new.

In Europe and Asia (as far as the latter portion of the continent is known) no volcano is found in a mountain chain, being more or less far from them. In the new world, on the contrary, the volcanoes, most stupendous for mass, form a part of the Cordilleras themselves. The mountains of Mica Slate and Gneiss in Peru, and New Granada, immediately touch the volcanic porphyries of the provinces of Quito and Pasto. To the south and north of these countries in Chili and in the kingdom of Guatimala, the active volcanoes are grouped in rows; they are the continuation of the chains of primitive rocks, and if the volcanic fire have broken out in some plains far from the Cordilleras, as in Mount Sangay and Jorullo, we must consider this phenomenon as an exception to the law which nature seems to have imposed on these regions.

The presence of a conical or dome-shaped figure is not essential to the volcano; it is sometimes extended in a ridge, in some parts smooth, in others rugged, and with pointed rocks. This latter structure is peculiar to Antisan, Pichinca, and two burning mountains in the province of Quito.

The following observations of M. Humboldt on Volcanoes are valuable :

1. Mountains, with slender conical peaks, have the most frequent and violent eruptions, as Cotopaxi, Teneriffe, and Orizava in Mexico.

2. With lengthened summits, more or less rugged, in small stony masses, are old volcanoes nearly extinguished. [nstances of this kind are found in Carguarazo, Pichinca, and perhaps Hecla in Iceland.

3. Rounded or dome-shaped summits, indicate doubtful porphyries, softened by fire and so thrown up, but never having flowed as liquid lava.

Illustrations of this third class occur in the majestic figure of Chimborazo, and the great Sarcony in Auvergne.

In order to form a better idea of the structure of volcanoes, their height has

Vesuvius (Von Buch) Etna

another, the circumference of the mouth of the crater much larger than at present, for Pliny describes it as including Monte Somma, hence the present one was raised within it. The size of the crater does not depend on that of the mountain, for Vesuvius, though less than one-fourth the

Teneriffe

Pichinca

1-3

In most volcanoes, the cone or sugarloaf preserves its form to the top; on ascending it, nothing obstructs the view to the interior of the crater; there are, however, exceptions to this, for the summits of the cones of Teneriffe and Cotopaxi are surmounted by a circular wall, appearing at a distance like a small cylinder placed on a truncated cone. According to Humboldt, this singular construction is seen in Cotopaxi three leagues off. In Teneriffe, the wall is so high that, but for a breach in it, apparently made by a current of ancient lava, the interior would be inaccessible.

The interior of the crater is generally conical, or funnel-shaped; the sides shelving inwards; the depth varies, as does also the circumference. The present greatest depth of Vesuvius is 700 feet, the circumference four miles and a half.

The interior presents a wild and frightful picture; the horrid gulf has a floor consisting of lava, (generally more or less solidified,) cinders, scoriæ, and enormous stones. In some parts the laya is still boiling, and from numerous cracks and fissures smoke and sulphureous vapour issue. In the centre, or nearer one of the sides, rises a much smaller cone; that of Vesuvius last summer was about 200 feet high, and within this is a second crater, from which flames, stones, &c. issue. These also happen, in many cases, from the sides of this second cone, and there are often several such inner cones. In descending into the crater, whilst the mountain is in a state of activity, it is essential to go, if possible, down the windward side, also to observe the direction of the wind whilst there. For, if it change, and blow the ejected hot cinders towards the path, a hasty retreat is often necessary. I descended into the crater of Vesuvius at 4 o'clock A.M., on the 31st of July, 1829, and, after remaining there more than an hour, the explosions became more violent, the wind changed, and I was obliged to return immediately.

The dimensions and appearance of volcanoes are constantly changing; thus, at one period, the depth of the crater of Vesuvius was only twenty-three feet; at

crater five times as great in diameter ;— that of Vulcano, though 1500 feet high, less than half the height of Vesuvius, has a crater as large. This, however, is not always the case, viz. that low volcanoes have the largest craters, for Cotopaxi and Rucupichinca have craters, according to Humboldt, as large as that of Vesuvius.

In a volcano like Vesuvius, where nearly all the force is directed towards the summit, the depth of the crater varies, but at the Peak of Teneriffe it would appear to have been stationary for a long time. In 1715, it was 115 feet (Mr. Eden); in 1805, 110 feet (M. Cordier); and subsequently less by M. Humboldt. The whole cone of a volcano is sometimes swallowed up in an eruption, leaving a crater nearly circular and of much larger dimensions. This is true of the celebrated Lake of Avernus near Naples, and of the neighbouring one of Agano; the cones having probably been buried after an eruption, or by its very frequent associate an earthquake. This is not surprising, when we consider that the crater is only the temporary roof of a much larger abyss; accordingly, we find it to return a hollow sound when struck

in some cases, as at the Solfaterra near Naples. It is even supposed that the Lago Bolsena, in which Pliny describes the floating islands, situated on the Sienna road, between Roine and Florence, was once a volcano, and pretty well authenticated that a lake on the side of it nearest to Rome was one.

Other instances are well known-as in a lake situated in a hollow at Albano near Rome, behind Pompey's Baths; and one at the Solfaterra, near Adrian's Villa, on the road to Tivoli. In such instances, the circumstance is sometimes more or less confirmed by the presence of so much sulphuretted hydrogen gas in the water, that birds are seen to fall dead into it in flying over it, and fish, &c. unable to live in it; and it is said that for ages, the only animal living in the Lago Averno, was a small species of aquatic animal, commonly called the sea-horse,* frogs also now abound in it—but no fish.

Lastly, in such instances, it is often interesting to observe how completely the character of the external features with

Here the lecturer exhibited a specimen.

pression; his half knit brow neither scowled defiance nor cowered as with fear, and the eye-beneath had not the sly leer of the fox or the fearless, cruel stare of the mastiff, yet there was a strange mingling of all. He was dressed in a green coat with large plated buttons, corded pantaloons descended to meet a short jockey boot, a silk waistcoat of a very showy pattern, and a blue and white silk handkerchief tied with a large knot nattily round his neck. He accosted me with a careless, saucy ease, which I could not help comparing with the humble servility and low bow which he gave to the magistrate on his entrance. (Perhaps the reader may say bows are to be expected at Bow Street, but I beg to inform him that this was not that farfamed place.) "Well, master, what's your business?" Having satisfied him, he bade me walk into the waiting room. This was a long and rather narrow apart. ment on the left of the passage, lighted by a single gas light from the centre, which developed its blackened walls, plastered with the sad evidences of human infamy and degradation, in the placards offering rewards for the apprehension and giving the description of the burglar, the felon, and the murderer. Here was an heterogeneous group-the prostitute and

For the Olio.

MR. EDITOR.-Business of rather a painful nature called me about a week since to one of the Metropolitan Police Offices, (that of identifying a man who had robbed me of some inconsiderable article, and who was brought up about a fortnight ago on a more serious charge.) It was a dreary day, the atmosphere was heavy, the drizzling rain was accompanied by a sharp chilly blast from the south-west; and the streets, sloppy and muddy, were deserted by all, save those whom necessity forced from their homes, or the miserable houseless wretches who, draggle tailed and shivering, sneaked beneath porch and window from the inclemency of the weather.

When I arrived at the office, the magistrate was not sitting, so having a little time on my hands, I, determined to see and observe, made my remarks, think. ing that if they were not of sufficient merit for the pages of your excellent Olio,' they might be for my portfolio. I was addressed by a fellow, from whose vulgar independence of manners, I concluded to be of that breed, termed Bow Street Runners.' Nature, or his villainous occupation, had stamped upon the man's face a peculiar and marked ex

suspected the policeman-the charley, and the pawnbroker, (called no doubt for the purpose of bringing some stolen property upon which he had lent money) Just before me was a meagre wretched object with an infant in his arms, and two others just starting into childhood clinging to his knees-the fixed tearless eye-the hollow dead-like cheek, and the head bent almost to the bosom, spoke eloquently of the misery and famine within; close beside him sat one-a woman-her eyes wandering vacantly and her flushed cheek fixed in the stupid grin of beastly intoxication, belching forth the reckless and incoherent creations of her excited imagination. Further on was a group of lads who could scarcely have attained their sixteenth year, anxiously conversing in low smothered tones; there was guilt and dismay in their faces, but nothing of sorrow or penitence.Close to these was a brazen masculine featured woman, costily though tawdrily attired; with violent gesticulations she was impressing something on a swarthy Jewish looking fellow, to which he ap peared to listen eagerly indeed; but the occasional shrug and the shake of his coarse black hair, of which he had not a little, as well as a word or two now and then audible-"it von't do"-" von't