a portion, from their surfaces, to the surrounding medium in which they are imbedded.

The degradation of these flint-stones is, likewise, strongly marked by a peculiar opacity, not unlike white glass-enamel or the superiór kinds of porcelain; and this forms a welldefined stratum, which covers entirely the whole surface of the stone, penetrating it to a greater or less depth. It cannot be considered as a very forced explanation, to say, that this may, probably, be the very point of contact, where this declension of silex is the commencement of a new modification; and that this terminates eventually in the perfection of a carbonate, or even of the lime itself, of which silex would then be considered as the independent progenitor.

That the blunted and nodular shape of the generality of siliceous stones, is a mark of loss in the primitive mass itself, may be explained by many examples. Thus, even in common experiments, a sharp or crystal-formed piece of any substance, capable of solution in an acid, soon loses its projecting corners, and, as the action of the acid proceeds, gradually becomes less indented, and more smooth or globular. It is rather a gratuitous conclusion, when the convex shape of pebbles, gravel, and all other siliceous stones, is ascribed to attrition: in some instances this argument may appear just, but in the more important cases it is, I conceive, extremely fallacious.

The true nature of clay, or, as it is now generally called, alumine, when considered as a primitive earth and simple element, seems very questionable; for, notwithstanding various methods have been employed to obtain it in a state of purity, still this doubt remains. Even, in one of the most celebrated systems of chemistry, after detailing the best mode to accomplish the end, the author adds, that the alumine "will then be nearly pure." One of the specific characters, peculiar to clay, tends very much to confirm this suspicion; it is that particular odour, constantly evolving from it, perceptible on all occasions, such as ploughing or stirring up land or garden-ground, and which is familiarly known by the term earthy smell.

It is true, there is also a flinty smell, or what the French call "odeur quartzeuse;" but this arises only when the flint is employed in the act of collision with steel, or against some kind of stone containing this scintillating ingredient, the silex; and, on such occasions, I have reason to believe, some new compound is the result, in which the presence of oxygen may be traced to this origin and to no other. The effect of flint upon steel is attended with this singular circumstance, that the particles which fly off are obedient to the loadstone, and consequently must be metallic; but, the metal is now deprived of its lustre and malleability, it is a compound, having imbibed a certain established dose of oxygen, at the expense of the silex, and the necessary caloric from the atmosphere.

If an ore consist chiefly of lime, silex and metal, and, if this metal be saturated with oxygen, the lime and, indeed, the whole compound be tastless and quite insoluble in water, what other inference can be drawn than this-that the silex alone is the ostensible and primary cause, both of the insipidity of the lime and the oxidized condition of the metal? Cases of this nature occur very frequently: the ore, which produces the new metal titanium, is precisely of that species; for it is composed of nearly equal parts of these three ingredients, and nothing more besides.

The quantity of silex in some ores, and in mineral substances containing acids and metallic oxides, is often very great; in others there is scarcely any: but we may occasionally trace it by its effects, and account for its absence from the condition of the ingredients left in the ore. In the following example, the quantity of silex remaining in the compound seems to be inversely as that of the oxygen, as if nearly the whole had been expended, and converted into the oxygen, which is now blended with the metals.

Thus, a specimen of wolfram, analysed by MM. Vauquelin and Hecht, contained in the hundred, 66 parts of tungstic acid, 18 of black oxide of iron, 6:25 black oxide of manganese, and only 1.5 of silex. Here, I would say, the whole of the oxygen had been generated entirely at the expense of the original silex, of which a very little or rather a mere surplus now remains in the ore. This is not only S 3

the

the most obvious source from whence the oxygen could have been derived, but, were there any objection, it must be also noticed that the ore itself had been originally enveloped in silex (gangue quartzeuse), so much so, that what was superfluous and extraneous adhered so closely, that it was with great difficulty these gentlemen could detach it, so as to divide it from the mere ore.

The sulphur, lime and metal, which often constitute the lead-ore, called galena, or sulphuret of lead, are accompanied by silex; and the general neutrality of the whole mixture may be ascribed to this, the common oxidizing element; for, if it be not in the ore itself, it is so very contiguous, that the matrix is, either entirely or in part, composed of this substance.

Magnesia, another of the most abundant of the earths, is never found in a pure state, but, like all others, is either blended with an acid or concealed by means of silex; and whether it be alone or accompanied by alumine, lime, or any other substance, this is invariably the state to which it is reduced. Thus, in asbestos, the magnesia, alumine and lime are sufficiently degraded to be deprived of all external peculiarities, and to shun the usual tests; for, though nearly one half of this mineral is composed of these three bodies, they are more than counterbalanced by the other element.

Potash and soda, which exist in somany situations, and are found to be more abundant than had formerly been suspected, appear to constitute one of the principal ingredients in various mineral bodies, particularly in the more huge masses of matter, in the primitive rocks and mountains, and, probably, in other substances, in which it has hitherto escaped our at tention. These are to be considered, not only to be in the same predicament as the earths, but, being possessed of higher powers and more considerable energy as salifiable bases, they furnish more conclusive examples for elucidating this subject, and more openly evince the oxgyenating efficacy. of silex. In all substances in which these are found, there is no appearance of an alkali; they have, till very lately, withstood all research; and even their ready solubility in water, the peculiar taste, which, it will be granted, is of the

most

most horrid causticity, and other qualities, which characterize these alkalis, are totally suppressed and softened into perfect inactivity.

Here, the same agency continues its operations; for, not merely the earths, the lime, or alumine, and metals, when they occur, but a considerable portion of alkali, amounting in some instances to more than one fifth of the whole, are all reduced into one mass of tasteless inoffensive stone. The leucite, which was analysed by M. Klaproth, contains about 6.22 of potash. 0.23 of alumine, and, 54 of silex; and from this, I confess, I can draw no other inference than,that the two salifiable bases are deprived of their primitive. characters, entirely by the other ingredient.

The proximity of all the carths to silex, and the constant association of this with one or more of the former, is a circumstance too notorious to dwell upon; and, considering the public utility of your pages, it were intrusive to multiply these examples, by bringing forward every case that may be suitable. We might really confide in almost a random selection; for all scientific books are fraught with proofs and analyses, in which silex, oxidized metals, neutral salts, or saturated substances, or, in short, where some modification of oxygen is indelibly impressed.

Even substances that apparently are independent of our globe are chiefly formed of silex; and the meteoric stones, which, in a highly ignited state, have occasionally been projected from the atmosphere upon various and distant places in the world, particularly in Yorkshire, and at Benares in the East Indies, even these contain about half their weight of silex; it has also been universally remarked, that these wonderful productions are always made up of the same elements of silex, iron, nickel, magnesia, and a small quantity of sulphur; and nearly in the same uniform proportions in all the specimens that have been analysed by other chemists since Mr. Howard, who first published the exact history of the composition.

These stones are, by many very intelligent men, supposed to have been ejected from some volcano in the moon; and though no one has positively asserted it, still the idea

has been fostered, and is generally treated with respect. Indeed, I see nothing very romantic in this opinion; and, in all cases, I think, when we are at a loss to explain, we may take the liberty to conjecture. One of the most celebrated chemists of the age, and whose correct knowledge of this and every other subject of science is indisputable, thus expresses himself upon this subject: "The opinion," says M. Vauquelin, "that these stones came from the moon, however extraordinary it may appear, is still, perhaps, the lcast unreasonable; and if it be true that no direct proofs. can be given, it is no less true that no well-founded reasoning can be opposed to it: the wiser way, therefore, is to own frankly, that we are totally ignorant of the origin of these stones, and of the causes which produce them." [To be continued.]

THE

LV. Proceedings of Learned Societies.

ROYAL SOCIETY.

HE meetings of this learned body, on the 14th and 21st of April, were occupied in reading an account of a shower of meteoric stones at Weston in North America. This account we have been enabled to lay before our readers in the present Number, by the kindness of the honourable Mr. Greville. It is by far the best authenticated and precise account of so singular a phænomenon that has yet been published in any country.

LINNEAN SOCIETY.

April 5. The right reverend the bishop of Carlisle, V. P. in the chair. A communication from Doctor Smith, the president, was read, entitled "Characters of a new Genus of Mosses called Hookeria, containing eight Species, &c." Some of these species are new, and others have heretofore ranked in the genus Hypnum; from which, however, the learned President pronounces them to be clearly distinguished by their reticulated capsules. These constitute an essential character for this new genus, all the species of which, however, accord in other characteristics. Dr. Smith has named