therefore, when philosophy has calmed the ardor with which we surveyed these stupendous phænomena-when we no longerregard them with stupid admiration, or abject terror-their 'Natural History' may be read with advantage; and facts may. triumph over theory, or the structures of a fertile imagination. The human mind, however, does not soon step down from its ardent flights; and the period is yet at some distance when fancy will not add to the number and increase the power of these burning projections. The abbé Ordinaire's researches have been extensive, and his work is in general a valuable one: yet he is deficient in some points that more modern inquiries might have supplied; and we are surprised that the scientific investigations of Kirwan, and the later philosophical observations of Spallanzani, escaped him. On the whole, indeed, this work is in some measure flimsy and superficial; but it contains some facts, of importance, and a collection of numerous observations not before brought together in so regular and pleasing a form,

The abbé describes volcanic mountains, and the inflammable substances which may feed their fires. He supposes that the existence of many apertures shows that the mountain will soon cease to be volcanic: but for this he offers no very satisfactory reason. He speaks of subterraneous fires where there are no explosions; but no where distinguishes with accuracy the causes of the explosion. His enumeration of those internal fires not attended by explosions is very full: that from M. Pallas we should have transcribed, had not the work been before us, both in the French and English versions. The abbé seems to support the theory of central fires, and to suppose that commotions in the earth may arise from these; so that in many places a volcano which might serve as a spiraculum would be beneficial. The remedy is however a very dangerous one; and we believe it may be greatly doubted, whether the causes are so nearly the same as the author, with others, has supposed; and the existence of central fires to any extent is very improbable.

The formation of mountains, M. Ordinaire contends with great justice, is not owing to volcanoes; for even the most singular volcanoes known at present were mountains before they exploded. In this disquisition he would have found an able assistant in Spallanzani. With equal reason, the opinion that all volcanoes are formed at the bottom of the ocean, and the mountains raised by their power, is rejected by our author. Why, however, volcanoes should be found only in the highest mountains, it is not easy to explain. The following reasons require the support of facts; yet they are as plausible as most others.

Mountains, like all the other productions of nature, have a regular conformity of parts: the dimensions of their mass are in due

proportion: I mean that we may always estimate the width of the sides, and the depth of the base, by the height to which the head of a mountain rises on the globe. The exceptions to this rule, for there are some, are very few in number.

We may add, that, of course, all the internal properties of which a concurrence is necessary to the forming of a volcano, such as fissures, caverns, a variety and abundance of inflammable matter, and a quantity of air and water, all in that case preserve similar proportions.

According to these plain observations, we shall not find in a mountain of an inferior order either bulk sufficient to contain and put in action what is necessary to produce a volcano of the first kind, which I have just mentioned; or depth enough for its base to reach, and still less for its sides to attract, the interior fires, commonly called central, and give existence to a volcano of the second kind.

But we can conceive without difficulty that the summit of a very high mountain, which in its descent takes an extension always increasing, probably down to its extreme internal base, may become a volcano either way. Etna extends itself nearly beneath the whole island of Sicily: what a prodigious lateral expansion, what dimeusions at its base must it have when it reaches its lowest internal foundation! As to its depth, we must suppose it very great; but where shall we presume that it stops?

If we consider the peak of Teneriffe, only from its summit to the level of the Atlantic ocean, how is it expanded even in that descent! Yet that is but its apparent base on the surface of the globe. Could we follow it to its interior foundation, how should we be astonished at its extent and depth !

It is easy to conceive that nature may either convert such prodigious masses into formidable arsenals, or employ them as firepumps in throwing out the subterranean fires, in order to relieve the bowels of the earth, and prevent a confusion over the whole surface of it.

I admit that all volcanoes are not so high as Etna, or the peak of Teneriffe; but we may consider these two as holding nearly the middle point on the scale of volcanic mountains. Many volcanoes are of their height: they are about a third lower than the highest, and certainly very few are a third lower than they are. r. 68.

Our author supposes that the mountains in the moon are higher than those on the earth, in a greater proportion than has been conceived; because the estimation of the latter commences from the level of the sea; while those of the moon have their measure commenced from their immediate bases: and he thinks that the volcanoes of the moon are in like manner considerable. He is somewhat at a loss to explain why submarine volcanoes should have no apparent elevation; but we know little of these, except when connected with burning mountains on an adjacent island, and cannot easily in any case measure their elevation. The sea is undoubtedly much deeper than has been supposed; for M. de la Place has shown that we must admit a hitherto unsuspected

depth, to be able to account for the phænomena of the tides from attraction.

The abbé next enumerates the many islands rendered unin. habitable by their volcanoes, and particularly notices the state of Iceland. The heat of simply hot water springs is, he thinks, owing to subterraneous fires, as well as the heat of all others which contain neither iron nor sulphur. It is singular that he should have overlooked the great heat of the Gieser fountain, which must be more than that of boiling water. This great degree it is compelled to bear from the compression, as it retains that heat after having been raised so high in the air. Kamtschatka is in the same latitude with Iceland, but in opposite longitudes, and equally subject to volcanic fires. Our author considers this as merely accidental; since the fires of volcanoes are, he thinks, in the external coats' of the earth. The abbé is of opinion that volcanoes render the neighbouring districts fruitful and healthy. This however has never been proved: they are not unusually sickly or infertile during the remission of the volcanic convulsions, nor are they peculiarly fruitful and healthy after them.

Here

Our author treats next of the cause of these commotions; and, though he speaks much of oils, bitumens, fermentations, &c. he rests the chief action on its true foundation-the powerful expansion of water when, by heat, it becomes steam. too Spallanzani, and even sir William Hamilton, would have assisted him. Various circumstances of an eruption are noticed in the following chapters. A description of such a phænomenon we shall select,

Let the reader figure to himself Vesuvius near four thousand feet high, Etna which is more than twelve thousand, Pichinca which is fifteen thousand, Cotopaxis or Antisana, which are eighteen thou sand; or, in fine, the insular volcano we have already mentioned, which was thought to exceed Chinboraço, and which, were it only equal to it, would still be nineteen thousand three hundred and ninety-two feet in height: let him imagine a column of fire of three or four miles in circumference, and sometimes more, whose height is more than double that of the mountain, rising from it with a thundering noise greater than that of all the cannon in the world discharged together. It seems as if it would set the sky on fire: lightnings flash from it. The dazzling brightness of its fire could not be endured by the eye, did not immense spiral clouds of smoke mode, rate its fierceness at intervals. These spread through the atmosphere, which they thicken; the whole horizon is covered with darkness; and at length nothing is to be seen but the burning summit of the mountain and the wonderful column of fire.

Its height, bulk, and explosion, result from the confinement in which the air had been kept within the volcano. Rarefied to the highest degree, forced on by the increasing heat of the immense pit, and pressed more and more by the prodigious fermentation of the

lava, the inflamed air, reduced to the size of the crater, at length escapes, spinning round and round. Breaking the top of the shaft, it bears it along in a thousand pieces, with soot, ashes, and pumice, with which the sides of the abyss within were loaded. In this horrible whirlwind it is even common to see huge pieces of calcined rock, torn from the bosom of the mountain, carried into the air.

The display of this phænomenon, in its extent and duration, depends upon the degree of force in the circumstances we have just mentioned. When the parts first raised lose this force, and, being left to their own weight, would naturally sink, those that come next, being still themselves supported, repel and throw them off. At that juncture an overspreading of the fire takes place at the top of the column, which adds to its beauty. I think it must have been from this view of it that the younger Pliny drew his comparison between the production of that eruption of Vesuvius, by which his uncle was killed, and of which he was himself an eye-witness, and the cypress tree.

In a short time the whole of the column turns into a horrible shower of red hot rocks, flints, and ashes. Monstrous burning masses are seen bounding, and rolling down the side of the mountain. Woe be to those places which lie in the direction of the wind prevailing at the time of this tremendous shower! Pompeii, Herculaneum, and Stabiæ, three towns to the south-west of Vesuvius, disappeared about seventeen centuries ago by a similar occurrence: and it was only in this century (the eighteenth) that they were discovered. A column, such as that we have been describing, broke over them, and the land about them: they were buried more than fifty feet under a mass of ashes and calcined flints, which was farther covered by a bed of lava several feet deep. If the wind be violent the ashes are carried to an incredible distance.' P. 125.

The ashes and other substances ejected by volcanic fires are various. The former were not however the cause of the dry fog in 1783, which seems to have been a phænomenon connected with electricity, though in what way is yet unknown. The other matters thrown out by volcanoes are sufficiently known; but the author has not detailed them scientifically. The flow of the lava is poetically described; yet the reader will observe that this wall of solid fire does not inflame a stick stuck into it, nor scorch the hand which holds the frying-pan-an experiment often tried over it.

The red hot

In this view it is a real river of fire at its source. lava issues in immense bubbles. It does not however become a rapid current even on the declivity of the mountain, but rolls heavily, being of a consistency, as we have already observed, very compact and adhesive. As it descends, the stream widens: it burns up every thing consumable by fire in its way. Its waves seem to be inexhaustible; they reach the plain in millions upon millions, often presenting to view a breadth of a mile and a half, and oft-times more. Here the following waves with difficulty press and impel those before: they rise one above the other in piles. At a certain distance from

the crater, when the air has made a sensible impression on the lava, it flows in a body from twelve to fifteen feet high, over which the stream is constantly collecting anew. It is a wall of solid fire; for to windward one may approach near enough to touch the matter with a pole, and try its resistance; although to leeward it is not to be borne within thirty paces without danger of suffocation. One might suppose that the top of these accumulated and moving bodies would concrete and become fixed, but it is not so: the dreadful heat they contain keeps them in a state sufficiently liquid to occasion the gradual rolling off of the mass; for it is in that manner that a stream of lava continues to run, and form a prolongation of this amazing wall. Five weeks after the eruption of 1794 the centre of the thickest part of the lava was red-hot. The progression of the matter thus continues as long as it is supplied from the crater, which does not cease disgorging until, after an emission more or less copious, the effervescence in the remainder of the matter contained in the gulf begins to subside. Then it still appears for some time bubbling at the rim of the crater, and afterwards contracts and sinks insensibly, till at last the mountain is restored to its usual calm.' P. 139.

The quantity of lava disgorged is immense; but the author does not recollect that it is very often porous, and that its specific gravity is inconsiderable. Among the matters ejected is sometimes water, when apparently this fluid is in greater proportion than the heat can convert into steam. It is an idle question to contest whether it proceed from the sea or reservoirs of fresh water. Each may occasionally supply the shower; and it is equally futile to dispute whether the matter discharged come from the middle or below the base of the mountain; for the question can never be decided.

The causes of the extinction of volcanoes are examined; but on these we need not enlarge, as many of them are imaginary. The extinction of the volcanoes in the Grecian islands in the Archipelago is attributed to the Euxine bursting through the Bosporus of Thrace a circumstance that cannot admit of proof, and on which the negative would be as probable as the affirmative. Some observations on the Giant's Causeway are subjoined; and the author discusses the question of these columns being volcanic somewhat superficially:-he leaves it undecided.

Several of the following chapters contain a catalogue of the different volcanoes hitherto known in different countries. It is, so far as our recollection reaches, complete; and, in some disputed mountains, the author's decisions seem to be judicious. Of these there are ninety-nine on the continents, and ninety in the islands. Seventy-eight of the former are in America. Of the continental volcanoes, a large proportion is near the sea. The connexion we can only explain from this circumstance— that subterraneous fires are not uncommon, but that a coincidence of water is necessary to produce the explosion. Let it