tain lavas, differing from innu- quantity, yet in some parts exmerable others, become basalti- hibits a kind of rade impe fect form; since, if this configuration prisms. depended on congelation, it must be found in all lavas when they had ceased to flow. The first writer, to my knowledge, who has adverted to this, is M. de Luc, who, in the second volume of his Travels, is of opinion that they have taken this regular figure in the sea, by the sudden condensation which took place on their flowing into it in a liquid state; other secondary circumstances, however, concurring, such as a greater homogeneity, and a certain attraction of their parts. "Of the same opinion is M. Dolomieu; though he does not deny that even porous lavas may sometimes, likewise, take the form of prisms. The former of these opinions is little less than hypothetic, while the latter is supported by facts too important to be cursorily stated. M. Dolomieu observes that all the currents of the lavas of Etna, the periods of which are preserved in history, have constantly experienced two effects in their congelation. Those which have cooled in the air, have divided, in consequence of the contraction they have suffered by the loss of their caloric (heat), into irregular masses; while all the others, which have precipitated into the sea, have, on their sudden congelation, contracted in a regular form, and divided into prismatic columns, which form they have only taken in the parts in contact with the water of the sea. Of this he met with evident proofs along the shore which extends from Catania to Castello di Jaci; and the famous lava of 1669, though unapt to the prismatic form, from. being spungy and little in "Among the objects to which I was attentive in my volcanic travels through the two Sicilies, the prismatic lavas were certainly not the last. While making the cir cuit of the Eolian islands of Etna and of Ischia, I constantly observed carefully the conformation of the stoney currents which fall into the sea. I have remarked, when treating of Ischia, that this configuration is frequently prismatic, and that the prisms are constantly formed in those parts of the currents which immerge into the water, and reach to a few feet above the level. This observation of mine certainly accords admirably with those of M. Dolomieu; the situa tion of these prisms clearly showing that they were formed at the time of the immersion of the lava into the sea, which, when it flowed, rose to where they begin to appear. But though I agree with him in this, I cannot in the remainder of my observations. Alicuda, as well as Felicuda, presents us with numerous currents and rocks that descend into the sea; and they are likewise found at Saline, Lipari, Stromboli, Panaria, Basiluzzo, and Vulcano; but these rocks and currents, which together extend over a space of more than sixty miles, do not afford the slightest indication of prisms. "As I went by sea from Messina to Catania, and returned to Messina from Catania, I had an opportunity twice to examine, at my leisure, that tract of shore, which, for the space of nearly threeand-twenty miles, is volcanic. One third of it, beginning at Catania, and proceeding to Castello di Jaci, consists of prisms more or less cha characterised, and such as they times trapezoidal pilasters, which have been described by M. Dolo-have been employed in buildings, mieu; but the other two thirds, Similar fissures are likewise obthough equally composed of lavas served in tufas, and earths of difwith the former, and for the most ferent kinds, and can never mispart falling perpendicularly into lead any person accustomed to the sea, have no such figure; and them, and acquainted with their only present, here and there, irre-true causes.' gular fissures and angular pieces, such as are, generally, observable in all lavas which separate more or less on their congelation. "In my circuit by sea round the shores of Ischia, I was particularly attentive, as I was every where else, to the conformation of the lavas; and here there seemed a great probability of finding them prismatic, from the abundance of them which in different directions and angles fall into the sea: but I have already observed, when treating of the island, and I now repeat it, that I did not find one with a regular form. "At Naples the prismatic, lavas of the currents of Vesuvius, under the park of Portici, have been much spoken of. When I made my observations on this burning mountain, I had not time to visit these lavas. It is with great pleasure, therefore, that I learn they have been examined by a person so well experienced in matters of this nature as the chevalier Gioeni undoubtedly is. But the celebrated prisms disappeared in the presence of so accurate an observer. The following is the account he gives; which is of considerable importance to our present subject:-'I wished to examine the basaltes which were pointed out to me as to be found on the sea-shore, under the royal park of Portici; but they proved to be only a 'compact lava, with perpendicular and extremely irregular fissures, forming quadrangular, and some "By this faithful relation of facts, I flatter myself, I have clearly shown that it cannot be supported as a general hypothesis, that flowing lavas take a prismatical confi. guration from the sudden coagulation they suffer on falling into the sea. "It may perhaps, be objected, that these prisms once existed in the lavas I observed, but that the irresistible violence of the waves, in a long series of years, has corroded and destroyed them. "Every person acquainted with the subject must immediately perceive how little solidity there is in this objection. I admit that the violence of the sea may, in some lavas, have totally destroyed these prisms; but that it can have had that effect on all, and through so extensive a space, is utterly improbable. Nor is it conceivable that Felicuda, among the Eolian isles, should still preserve its prisms perfect, while the rest of those islands have entirely lost theirs, notwithstanding they are all equally exposed to the shocks of the waves. "I cannot bere omit another remark. It is certain that more than one of these islands were not formed by one eruption, but by successive ejections of lavas accumulating on each other; and in some deep fissures, occasioned by the sea, this successive formation is discoverable by the eye, as we may perceive five or six different strata of lava one above the other. The internal strata, in very remote pe riods, having flowed into the sea, as the external flowed afterwards; it is evident that, if the latter, on touching the water, became prismatic, the same change must have taken place, also, in the former; which being defended from the injuries of the sea, by the external strata, must still preserve their prismatic configuration, of which, however, no traces remain. We must, therefore, conclude that innumerable lavas may fall into the sea, without having their external appearance in the least changed by the sudden congelation which then takes place? "That the prismatic configuration of lavas is not always the effect of their immersion in the waters of the sea, likewise appears from many of them taking the same form in the air; of which we have a disti. guished example in the crater of Vulcano. Here, certainly, we cannot suqpose any intervention of the waters of the sea. Similar ob. servations have been made on Mount Etna by the Chevalier Gioeni. I have observed,' says he, in the work before cited, ba⚫ saltic columns, at the summit of Etna, and nearly on a level with the base of its vast crater, where there is certainly no probability of the sea ever having reached; and I have frequently found polyhedrous basaltes perfectly cha'racterised in excavations made by men in the centre of lavas, 'which have issued from the sides of Mount Etna, in periods much posterior to the retiring of the 'sea.' "I should, however, appear deficient in candour, did I not mention that M. Dolomieu admits that lavas may, sometimes in the air, assume the prismatic form, if they fall into clefts and fissures where they sud1798. denly cool, of which he adduces an example in the islands of Ponza. "I shall only remark, that I do not perceive the absolute necessity of the fissures in this case; since we frequently find lavas with this configuration in perfectly open places; as I have seen in the great mouth of Vulcano. And with this opinion the observations of Gioeni on Etna certainly accord; for, had he remarked the concurrence of such a circumstance, he, undoubtedly, would have mentioned it. "What conclusion, then, ought we to deduce from all these facts and observations ? "First that many basalti-form lavas have assumed this organisation on coagulating within the sea. "Secondly that others have taken the same form, merely in cooling in the open air. "Thirdly that innumerable other lavas have not taken this figure, either in the sea or in the air. "It appears, at first view, that these differences depend on the different nature of the lavas themselves. This opinion, at least, is rendered probable by what we observe in earths penetrated with water, which, in drying, take, more or less, prismatic forms, as has been observed frequently in the argillaceous kinds. I have seen, when a turbid torrent has been introduced into a ditch through an argillaceous marle, the latter, in drying, divide into polyhedrous pieces; but when the water passed through chalk, or calcareous marle, the greater part of the pieces were amorphous. When we however observe lavas with requisite attention, this conformation in them seems to be effected differently. "It has already been said, that several of the prismatic lavas of Felicuda H Felicuda have for their base shoerl cations? These I will endeavour in mass; but it is true that other congenerous lavas of the same island, which form as it were walls perpendicular to the sea, are smooth over their whole superficies. A similar smoothness is observatie in some of those of Mount Etna, on the shore between Messina and Catania, which have for their base the horn-stone; though others extremely resembling them, between Jaci Reale and Catania, are formed in prisms. to suggest, illustrating my conjecture by the two cases above adduced; the one, that of the lavas which take the form of prisms merely from the contact of the atmosphere, as in Vulcano and near the summit of Etna; the other, that of the lavas which refuse to take such a form even within the sea, as at Ischia, in some parts of the base of Etna, and in all the Eolian isles except Felicuda. As to the former, may not a sud"Compactness and solidity are, den coagulation and contraction likewise, not a necessary condi- have taken place in some lavas tion in lavas, to this appropriate from the mere influence of the atcrystallization. This has already mosphere, though the lava was not been remarked by M. Dolomieu; included in any cleft or fissure? and I have observed that many It is sufficient that it be suddenly amorphous lavas on the shores of deprived of the caloric (heat) several of the Eolian islands are more compact than the prismatic lavas of Felicuda. "What then can be the intrinsic circumstance of the lava which determines it thus to cleave in the prismatic form? I confess I am ignorant: and who can say that we do not seek it in vain within the lava, since it may be extrinsic and adventitious? Such, certainly, appears to be the opinion of M. de Luc; and, more expressly, that of M. Dolomieu, who, to explain the phenomenon of volcanic prisms, has recourse to a sudden congelation, and instantaneous contraction of lavas. "The facts which we have adduced relative to lavas, both pris. matic and not prismatic, it has been seen, do not always accord with those related by the French naturalist. But even on this supposition, which is incontestable, may we not retain the same principle of explanation, which, to say the truth, appears to be sufficient, with some requisite modifi by which it is penetrated, and which rendered it rarefied and fluid. To this deprivation a lava of little thickness will be very liable; since a body loses its beat the sooner, the less its thickness and density. This sudden contraction may also be produced by the circumstances of the atmosphere; as should a strong wind, of a very cold temperature, blow at the time the melted lavas in our crucibles will be found to give greater weight to this latter conjecture. If they are taken from the furnace, and caused to pass through a heat gradually less; their surface as they cool, will only split into a few cracks, of little depth, and usually irregular; but, when they are immediately, in the winter time, carried into the cold air, the fissures, besides being deeper, will frequently be disposed in such a manner, as to form small polybedrous prisms, which may easily be detached from the rest of the lava. "With respect to those lavas which do not assume a prismatic form, though they fall into the sea, it is certain that, to take that conformation, their mass must have a strong degree of effervescence and dilatation, and that it must be deeply penetrated with the igneous fluid, otherwise the contraction necessary to produce prisms cannot take place. But many currents which descend from the summit of burning mountains to the sea, must have lost their effervescence with their heat in so long a course, and scarcely retain sufficient to continue their motion downwards, which, perhaps, would cease, were it not for the impelling gravity of the lava, which frequently falls into the sea perpendicularly. "Such is the hypothesis by which I would explain the cause why some lavas have assumed a prismatic conformation without any concurrence of the sea-water, and others exhibit no appearance of it in places where they have im merged into the sea. I neverthe less leave every one to form his own opinion; and should an explanation of these important facts be discovered, preferable to mine, which I consider as only conjectural, I shall receive the communication of it with sincere gratitude, and adopt it with pleasure." GEOLOGICAL FACTS, Corroborative of the MOSAIC ACCOUNT of the DELUGE, with an INQUIRY into the ORIGIN, PROGRESS, and still PERMANENT CONSEQUENCES of that CATASTROPHE, by RICHARD KIRWAN, ESQ. LL.D. F.R.S. and M.R.I.A. [From the sixth Volume of the TRANSACTIONS of the ROYAL IRISH ACADEMY.] 1st. on a mountain in Peru at the height of 14,220 feet, 2 Buff. Epoque, 268. Now I have already shewn, that no mountains higher than 8,500 feet were formed since the creation of fish, or, in other words, that fish did not exist until the original ocean bad subsided to the height of eight thousand five hundred feet above its present level. Therefore the shells found at more elevated stations were let there by a subsequent ioundation. Now an inundation that reached such heights could not CCORDING to Don be partial, but must have extended AUlloa, shells were found over the whole globe. "2dly, The bones of elephants and of rhinoceri, and even the intire carcase of a rhinoceros, have been found in the lower parts of Siberia. As these animals could not live in so cold a country, they must have been brought thither by an inundation from warmer and very distant climates, betwist which and Siberia mountains above nine thousand feet high intervene. It may be replied that Siberia, as we have already shewn, was not originally as cold as it is at present; |