^{page 44 note *} Particular reasons induced me not to publish this paper at full length; but; wishing to preserve a record of some opinions peculiar to myself which it contained, I introduced a short abstract of it into the History of the Transactions.

^{page 46 note *} In the course of last winter, when I first thought of resuming my experiments, I proposed to this gentleman, that, in imitation of a practice, common in the Academy of Sciences of Paris, we should perform them in company. To this proposal he cheerfully agreed; but, before any experiments had been begun, he found himself so much occupied by professional duties, that he could not bestow upon the subject the time which it necessarily required; and we gave up the idea of working in company.

^{page 46 note †} In characterising the particular specimens, I have adopted, with scarcely any variation, descriptions drawn up by Dr Kennedy, whose name I shall have occasion frequently to mention in the course of this paper. In the employment of terms, we have profited by the advice of Mr Deriabin, a gentleman well versed in the language of the Wernerian School.

^{page 47 note *} Called Bell's Mills Quarry.

^{page 48 note *} I showed this result at a meeting of the Society on 5th of February.

^{page 50 note *} The measurement of the temperatures may be relied upon as accurate; they were determined by two sets of pieces, one purchased by me during the lifetime of the late Mr Wedgwood, and the other likewise made by him, belonging to Dr Kennedy. The two sets correspond exactly; and Dr Kennedy's had, at his request, been carefully examined by the present Mr Wedgwood, who found them true by his father's original standard.

^{page 56 note *} Though I differ widely from this gentleman in many of his theoretical opinions, I cannot too strongly express my admiration of his merit as a natural historian. His descriptions of countries, as well as of minerals, present the most lively representations to the mind of the reader, which, in the numerous instances I have witnessed, are perfectly correct.

^{page 59 note *} None of the lavas I have seen contained the smallest vestige of petroleum; nor did I meet with any sulphur but what was evidently produced by the condensation of vapours, rising through crevices, long after the eruptions had ceased.

^{page 59 note †} I conceive, therefore, that the formation of the insulated substances contained in lavas, as well as the other peculiarities of internal structure, possessed by lavas in common with granite and basaltes, must be ascribed in all of them to crystallization during slow cooling after fusion, as I stated formerly in Spring 1790, (Trans. Edin. vol. III.). The year following, Dr Beddoes presented to the Royal Society of London a paper, in which he also explains the character of granite and basaltes by crystallization, in consequence of slow cooling.

^{page 60 note *} “Elle est formée d'une pâte de roche de corne grise, à grains sins, mêlée d'écailles, et de cristaux de seld-spath de même couleur; elle contient un très grand nombre de cristaux de schorl noir, et de grains de crysolites jaunes, les uns et les autres quelquefois chatoyans, de différentes couleurs dans leurs fractures.——————— Cette lave a une cassure seche, et un grain rude, surtout dans le centre des courans; c'est là où elle a toujours conservé une couleur plus claire, qui doit être celle de sa base; fur les bords es les surfaces elle s'est sort noircie; elle y a acquis une assez forte action sur l'aiguille aimantée que celle du centre n'a presque point.”

^{page 61 note *} “Lave homogene noire: son grain est fin et serré, il est un peu brillant, comme micacé lorsqu'on le présente au soleil; sa cassure nette et seche est conchéide comme celle du filex.”

^{page 61 note †} It belongs to the fifth variety of his compact lavas.

^{page 62 note *} M. Dolomieu ascribes the formation of part of Mount Ætna itself to a similar cause. I shall have occasion, in another part of this paper, to consider that opinion.

^{page 66 note *} As at Malpertui above Piedimonte.

^{page 66 note †} An account of Dr Kennedy's analysis is published in this volume.

^{page 67 note *} Though chemists have hitherto overlooked, in their experiments, the mode in which bodies were cooled after being reduced to a state of fusion ; yet many results, which we are now entitled to ascribe to slow cooling, have been occasionally observed. The flag of a furnace bears a strong resemblance to what we have called the liver crystallite, and is probably formed in the same manner. I have seen a mass possessing, in a great measure, the stony character of whins and lavas, which was produced in a lime-kiln by the fusion of an impure limestone; and Dr Beddoes has observed a crystallized texture in the flags of some iron furnaces. I am informed, that the celebrated Mr Klaproth has described some striking examples of crystallization after fusion, which he obtained in exposing various substances to the heat of the porcelain surnace at Berlin.

^{page 67 note †} It may be asked, what has become of this superincumbent mass; and by what means it has been removed. Dr Hutton answers, that it has been gradually worn away during an immense course of ages, by the action of those causes which continue, under our eyes, to corrode the surface of the globe: That the solid parts, being conveyed to the bottom of the ocean, are there deposited in beds of sand and gravel, which, in some future revolution, being exposed to heat, may be again converted into stony strata.

The whole of this system appears to me well founded, except in what regards the removal of the superincumbent mass, which has been performed, I conceive, in a very different manner. I am inclined to agree on this point with M. Pallas, M. de Saussure, and M. Dolomieu, and to believe that, at some period very remote with respect to our histories, though subsequent to the induration of the mineral kingdom, the surface of the globe has been swept by vast torrents, flowing with great rapidity, and so deep as to overtop the mountains; that these torrents, by removing and undermining the slrata in some glaces, and by forming in others immense deposits, have produced the broken and motley structure, which the loose and external part of our globe every where exhibits.

In the Alps and in Sicily I have witnessed several of those curious facts, upon which M. de Saussure and M. Dolomieu found their opinion, and which seem to justify their conclusions. I have likewise observed, in this country, many phenomena which denote the influence of similar agents. Lord Daar, who joins me in agreeing with Dr Hutton in almost every article but this, has added great weight to the argument by some general observations on lakes, and by some very interesting facts which he has observed in the Highlands of Scotland. We propose to pursue this subject, and to lay the result of our inquiries before the Society. Dr Hutton, in the second volume of his Theory of the Earth, has taken great pains to refute all that has been said about these torrents; but, in my opinion, their existence is not only quite confiftent with his general views, but seems deducible from his suppositions, almost as a necessary consequence. When the strata, according to his system, were elevated from the bottom of the sea, the removal of so much water, if not performed with unaccountable slowness, must have produced torrents, in all directions, of excessive magnitude, and fully adequate to the effects I have thus ascribed to them.

^{page 68 note *} The modifications of the action of heat, occasioned by pressure, which have been taken into account by no geologist but Dr Hutton, distinguish his theory from all other igneous theories.

^{page 70 note *} M. Dolomieu has observed this distinction; but supposes that the masses which we conceive to have flowed subterraneously were erupted at the bottom of the sea.

^{page 71 note *} I saw this place in company with Dr J. Home in 1785.

^{page 71 note †} M. Dolomieu conceives these lavas to have flowed over the lips of the crater, (Isles Ponces, p. 100.); M. Breislack, that they had first filled the open cavity of the crater, and from thence had flowed into crevices formed in its sides, “che una lava avendo riempita la cavita del cratere si sosse infinuata per queste senditure,” (Topografia Fisica della Campania, p. 115.). This last mentioned work, published in 1798, contains many interesting and accurate descriptions. Should the circumstances of the times permit, the author will have it in his power to follow out, with every advantage, the hints I have suggested.