rate, and another plane ftill lefs will be applied to the one al ready generated. Others will fucceed, each gradually and fym metrically diminishing, till they terminate in a fingle molecule, forming the vertex of a pyramid, elevated, by the influence of this law of decreafe, upon one of the planes of the original folid; and if the fame law has operated on the other planes, each of them will be crowned with a fimilar pyramid.

Such would be the operation of a decreafe, by one row of molecules on the edges of the planes. It may take place on the angles, instead of the edges. It is not confined to a decrease of one row of molecules only; for the decreafe may take place, by two or three rows in breadth, and one in height; or by two or three in height, and one in breadth. More than one of these laws may operate at the fame time, in modifying the fame nucleus; and, after the operation of one has reached a certain extent, it may be fufpended, and the fecondary form of the cryftal be completed by the action of another. In short, any, or all of thefe laws, may operate at the fame time, or in fucceffion, on the fides and angles of the fame nucleus.

Let it not be objected to this theory, that the fplendid polish with which the furfaces of crystals are frequently adorned, could never refult from the steps with which the decrease of the molecules must furrow their fides. We must not force any analogy between the groffhefs of our mafonry and the architecture of na ture. The molecules, of which crystals are compofed, are, to our fenfes, infinitely fmall; and the step, formed by the decrease of one, two, or three rows of molecules, must be to us imperceptible.

Let it not be objected either that the admiffion of the laws of decrease is unphilofophical; becaufe, from their variety, from their partial operation, and the facility with which any, or all of them, are reforted to, they appear capable of deriving any poffible form from any conceivable nucleus. To this M. Huy h's provided a reply. By an ingenious application of his mathematical fcience, he has not only calculated the laws, by which the known fecondary forms of all cryftals may be generated, but he has demonstrated, that it is impoffible, by any law of decreafe, to derive certain fecondary forms from particular integral molecules; and this demonstration is the more important, as, in feveral inftances, it precludes the pofiibility of confounding fubftances effentially different, which the ambiguity of their other external characters might have caufed to be erroneously affociated.

Where the induftry and dexterity of M. Haüy have failed, in mechanically extracting the integral molecule, he has difcovered its form, by an inverfe operation of the calculations that would have

have determined the fecondary forms, had he been put in poffeffion of the primitive one. The geometrical propofitions, by which the accuracy of his deductions is demonftrated, are given at length by M. Haüy: the particular propofitions relating to each fpecies, accompany the defcriptions of the mineral to which they belong: he has rendered the defcription of cryftalline forms fimple and precife, by applying to it ingenious reprefentative figns; and he has devifed a nomenclature, in which almoft every known crystal is distinguished by a specific denomination.

It is not from fo fhort and imperfect a sketch, that the merits of a fyftem, so various in its relations, and fo complicated in its detail, can be properly appreciated. It appears to us to have enriched mineralogy with the only unerring external character, and to prefent an infallible criterion for determining the mineralogical fpecies. We need no longer reluctantly rely on the difcordant refults of analyfis, nor allow ourselves to be bewildered by the intermixtures of colour, by indeterminate fracture, or varying fpecific gravity. We are poffeffed of a character impreffed with mathematical accuracy, which no illufive appearances can conceal; which our wilfulness cannot vary, nor our ignorance mistake.

Analyfis, locality, and other external or internal characters, enable us to affociate to the perfect crystal, the abortions of difturbed crystallization, and the amorphous maffes in which minerals are most frequently found. Even here, the laws of cryftallization frequently apply; and the integral molecule may be extracted by mechanical divifion, from an apparently unarranged mafs. To the few fubftances that are as deftitute of regularity in their internal structure, as in their external form, the ufual modes of investigation must still be applied.

It is in the determination of the fpecies, that the interefts of philofophy are most concerned. The manner in which they are afterwards grouped into genera, or claffes, is comparatively unimportant; and as its utility wholly confifts in directing us where to feek for the fpecies we are in queft of, it may be safely refigned to the caprice of each fabricator of a system, provided its arrangement does not violate any established law, or militate against any acknowledged fact. The impropriety of claffing minerals ftrictly, according to the proportions of earths they contain, as determined by analytic experiments, feems to be fufficiently proved by the uncertainty attached to fuch investigations. The progrefs of fcience has feen minerals repeatedly transferred from one genus to another, to the no fmall embarrassment of thofe whofe knowledge of a mineral is confined to the relative pofition its name occupies in the columns of the fyftem which they honour by their approbation. A fyftem which would re

quire talc to be divided into two fpecies, because it is fometimes found to be utterly divefted of the magnesian earth, which, upon other occafions, is esteemed its moft effential component, may have been established in the infancy of fcience, and continued through defpair of devifing one lefs objectionable; but its exiftence ought to ceafe with the ignorance which fanctioned it.

Perfectly aware of the difficulties under which the old divifion laboured, M. Haüy has diftributed minerals by a method, the fimplicity of which leaves it little liable to objection. His first clafs confifts of the combinations of earths and alkalies with acids. The fecond clafs confifts of the combination of earths with earths; sometimes united with an alkali. The third clafs confifts of combuftible fubftances not metallic. The fourth clafs, of metals, arranged according to their oxidibility and reductibility.

In the description of each fpecies, after ftating the name by which he wishes it to be diftinguished, and its fynonymes, M. Hauy proceeds to confider its effential character, derived from the moft prominent, unvarying, and definite of its internal and external characters.

In confidering the geometric character, the primitive form is given, together with the value of its angles. The greater or lefs facility of obtaining the nucleus by mechanical divifion is stated, and the direction of the natural joints is indicated.

He proceeds to examine the phyfical characters, comprehending fpecific gravity, relative hardness, fracture, magnetic and electric relations, refraction, phofphorefcence, tenacity, &c.

Its chemical character comprehends the action of the blowpipe, and of acids; and gives the refults of the analysis in which the greatest reliance can be placed.

Thefe compofe the specific character of each fubstance, and are diftinguished by their invariability, from the diverfity of forms it may exhibit, the colours with which it may be decorated, and the variable degree of its tranfparence.

In investigating the forms which any mineral affumes, those which are determinable are first examined. This term includes all crystals capable of geometrical defcription. Each is diftinguifhed by the name which has been defignated in the nomenclature of crystals to reprefent that particular variety; the value of its angles are indicated; and, if the structure is complicated, the ne ceffary elucidations are given.

The indeterminable forms are next noticed. They comprehend the refults of disturbed or rapid cryftallization, and all thofe minerals that are stalactitic, globular, granular, or wholly amorphous. The varieties of colour, and degrees of tranfparence, are next atVOL. III. NO. 5.

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tended to. The diftinctive characters which effentially facilitate the examination of minerals, by pointing out wherein they differ from the fubftances to which they bear a general refemblance, are detailed with remarkable perfpicuity and precifion. Each article is terminated by annotations on the geological relations of the fubitance, and obfervations on its utility in medicine, or in the

arts.

This rigorous examination of minerals, and inquiry into relations hitherto imperfectly developed, has led M. Hay to make very important changes in the diftribution of the fpecies. Not a few, which appeared with diftinction in former fyftems, are now reduced to varieties; and not a few fpecies, which appeared too comprehenfive, have been fubdivided. Many mineralogifts will ftart at finding chalcedony, jafper, hornftone, and opal, united to the fpecies of quartz; and will be almost equally amazed to find zeolyte fubdivided into méfotype, ftillbite, analcime, and chaba

fie.

It would far exceed our limits, to enter into a disquisition on individual alterations; yet it is proper to express our general opinion of their propriety. After recovering from the fhock occafioned by the overthrow of our previous affociations and preju dices, we have commonly acceded to them; and almost always, on extending the inveftigation, we have enjoyed the fatisfaction of yielding an unqualified affent.

The innovating hand of M. Haüy has not been confined to thefe changes; for his reader will find, that the entire nomenclature of mineralogy has been altered, and that scarcely one of his old acquaintances bears the denomination by which it was formerly diftinguished. Of all the alterations he could poffibly devife, this is the one which must prove the moft intolerable to veteran mineralogifts. It is moft offenfive to the felf-love of many, to the prejudices of others, and to the indolence of all. The difcoverers, who have bestowed fome favourite denomination on the fubftance they have introduced to public notice, and perhaps have given it their own name, or prevailed on their friends to give it, will be not a little irritated to find this child of adoption torn from them, and announced to the public under another appellation, which, to their ears, must sound most barbarous. Those whose attachment to fyftem and establishment renders all innovations fufpected and difagreeable, will feel their indignation not a little excited; and all will find it an unpleafant exertion, to obtain a knowledge of thefe new names, and to acquire the habit of affociating them readily with the objects they reprefent. Aware, as M. Haüy must have been, of the general difquiet the change of nomenclature could not fail to produce, he ought to have potent arguments to justify his adoption of fo unpopular an alteration. Let us examine his inducements.

All

All fyftem-mongers feem to be affected by a troublesome propenfity to neology, and have erroneously imagined that there is as much merit in fabricating a word as in difcovering a fact. They feem to think that the grandeur and novelty of their language may give an afpect of originality and fublimity to their hypothefis, and that the obfcurity in which their phrafeology may involve it, will render it more difficult to affail. Frequent failures have not convinced them of the fallacy of thefe ideas; and almost every theory, from the phlogistic one of Stahl to the tranfcendental one of Kant, has been diftinguifhed by an almoft entire change in the names of the fubjects to which it related. Thefe changes, however, are fometimes neceffary; and the old mineralogical nomenclature will be found to contain numerous inftances of names that effentially needed reform.

The new chemical nomenclature has been fanctioned by the approbation of all Europe; and it would be abfurd to object to its extenfion to mineralogy, in every inftance where it could be confiftently applied. It is certainly much better to talk of sulphate of barytes, than of ponderous fpar; of photphate of lime, than of apatite; and of fulphate of ftrontites, than of schützite, by which the Germans have chofen, with their ufual difregard of euphony, to distinguish that mineral. Sulphuret of lead is more intelligible than galæna; phosphate of lead, than either green or brown lead; and molybdate of lead, than yellow lead ore. Thefe names can only be difagreeable to those who are ignorant of every thing about a mineral except its mere external appearance, and the appellations by which they have been accuftomed to diftinguifh it; for its chemical name must be fuggefted by a knowledge of its compofition.

As far as the adoption of the chemical nomenclature extends, we moft heartily agree, therefore, with M. Haüy's reform; but there is a very numerous clafs of minerals compofed of earths combined with earths, with or without a metallic oxide, and with or without an alkali. No modifications of language can defcribe the compofition of these fubftances, without extending the name to an immeafurable length, and without the greatest confufion, from the fimilarity of compofition in very different minerals. To fuch fubftances, therefore, a fpecific denomination must be applied; and M. Hatiy found fo many defects in the old nomenclature, that he has almost entirely changed it.

Where two minerals were affociated, in his fyftem, that had formerly been considered as dillinct, it fometimes was requifite, to prevent mistakes, to fubftitute one new naine in place of the two old ones; and it was abfolutely neceflary, when a former

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fpecies