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rate, and another plane ftill less will be applied to the one als ready generated. Others will succeed, each gradually and fym. metrically diminishing, till they terminate in a Gingle molecule, forming the vertex of a pyramid, elevated, by the influence of this law of decrease, upon one of the planes of the original solid; and if the same law has operated on the other planes, each of them will be crowned with a similar pyramid.

Such would be the operation of a decrease, by one row of molecules on the edgos 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 decrease may take place, by two or three rows in breadth, and one in height; or by two od three in height, and one in breadth. More than one of these laws may operate at the same time, in modifying the fame nucleus; and, after the operation of one has reached a certain ex. tent, it may be suspended, and the secondary form of the crystal be completed by the action of another. In short, any, or all of these laws, may operate at the same time, or in succession, on the Gides and angles of the same nucleus.

Let it not be objected to this theory, that the splendid polish with which the surfaces of crystals are frequently adorned, could never result from the iteps with which the decrease of the molecules muit furrow their Gdes. We must not force any analogy between the groitness of our masonry and the architecture of na. ture. The moleculcs, of which crystals are composed, are, to our senses, infinitely mall; and the step, formed by the decrease of one, two, or three rows of molecules, must be to us imperceptible.

Let it not be objeded either that the admission of the laws of decrease is unphilosophical; because, from their variety, from their partial operation, and the facility with which any, or all of them, are resorted to, they appear capable of deriving any possible form from any conceivable nucleus. To this M. ILü; h's provided a reply. By an ingenious application of his inithematical science, he has not only calculated the laws, by which the known fecondary forms of all crystals may be generated, but he has demonitrated, that it is importible, by any law of decrease, to dee rive certain secondary forms from particular integral molecules; and this demonitration is the more important, as, in several inItances, it precludes the posibility of confounding subítances ef. sentially different, which the ambiguity of their other external characters might have caused to be erroneously associated.

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

have have determined the secondary forms, had he been put in poffefGon of the primitive one. The geometrical propositions, by which the accuracy of his deductions is demonstrated, are given at length by M. Haüy: the particular propositions relating to cach species, accompany the descriptions of the mineral to which they belong: be has rendered the description of crystalline forms fimple and precise, by applying to it ingenious representative signs; and he has devised a nomenclature, in which almost every known crystal is diftinguished by a specific denomination.

It is not from so short and imperfect a sketch, that the merits of a system, so various in its relations, and so complicated in its detail, can be properly appreciated. It appears to us to have enriched mineralogy with the only unerring external character, and to present an infallible criterion for determining the mineralogical species. We need no longer reluctantly rely on the discordant results of analysis, nor allow ourselves to be bewildered by the intermixtures of colour, by indeterminate fracture, or varying (pecific gravity. We are poffefsed of a character impressed with mathematical accuracy, which no illusive appearances can conceal; which our wilfulness cannot vary, nor our ignorance mistake.

Analysis, locality, and other external or internal characters, enable us to associate to the perfect crystal, the abortions of difturbed crystallization, and the amorphous masses in which minerals are most frequently found. Even here, the laws of crystallization frequently apply; and the integral molecule may be extracted by mechanical division, from an apparently unarranged mass. To the few substances that are as deftitute of regularity in their internal structure, as in their external form, the usual modes of investigation must still be applied.

It is in the determination of the fpecies, that the interests of philosophy are most concerned. The manner in which they are afterwards grouped into genera, or classes, is comparatively unimportant; and as its utility wholly confifts in directing us where to seek for the species we are in quest 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 classing minerals strictly, according to the proportions of earths they contain, as determined by analytic experiments, seems to be sufficiently proved by the uncertainty attached to such investigations. The progress of science has seen minerals repeatedly transferred from one genus to another, to the no small embarrafsment of those whose knowledge of a mineral is confined to the relative position its name occupies in the columns of the system which they honour by their approbation. A system which would re

quire talc to be divided into two species, because it is sometimes found to be utterly divested of the magnesian earth, which, upon other occafions, is esteemed its most essential component, may have been established in the infancy of science, and continued through despair of devising one less objectionable ; but its existence ought to cease with the ignorance which sanctioned it.

Perfectly aware of the difficulties under which the old division laboured, M. Haüy has distributed minerals by a method, the fimplicity of which leaves it little liable to objection. His first class conärts of the combinations of earths and alkalies with acids. The second class conäists of the combination of earths with earths ; sometimes united with an alkali. The third class consists of combustible substances not metallic. The fourth class, of metals, arranged according to their oxidibility and reductibility.

In the description of each species, after stating the name by which he wishes it to be distinguished, and its synonymes, M. Haüy proceeds to consider its essential character, derived from the most prominent, unvarying, and definite of its internal and external characters.

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

He proceeds to examine the physical characters, comprehending specific gravity, relative hardness, fracture, magnetic and electric relations, refraction, phosphorescence, tenacity, &c.

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

These compose the specific character of each substance, and are distinguished by their invariability, from the diversity of forms it may exhibit, the colours with which it may be decorated, and the variable degree of its transparence.

In investigating the forms which any mineral assumes, those which are determinable are first examined. This term includes all crystals capable of geometrical description. Each is diftinguished by the name which has been designated in the nomenclature of crystals to represent that particular variety; the value of its angles are indicated; and, if the structure is complicated; the ne. ceflary elucidations are given.

The indeterminable forms are next noticed. They comprehend the resuks of disturbed or rapid cryftallization, and all those minerals that are stalactitit, globular, granular, or wholly amorphous. The yarieties of colour, and degrees of transparence, are next atVOL. II. NO. 5:

tended

tended to. The distinctive characters which essentially facilitate the examination of minerals, by pointing out wherein they differ from the substances to which they bear a general resemblance, are detailed with remarkable perfpicuity and precision. Each article is terminated by annotations on the geological relations of the substance, and observations on its utility in medicine, or in the arts.

This rigorous examination of minerals, and inquiry into relations hitherio imperfectly developed, has led M. Haüy to make very important changes in the distribution of the species. Not a few', 'which appeared with distinction in former systems, are now reduced to varieties; and not a few species, which appeared too comprehensive, have been subdivided. Many mineralogists will ftart at finding chalcedony, jasper, hornstone, and opal, united to the species of quartz; and will be almost equally amazed to find 2eolyte subdivided into nélotype, stillbite, analcime, and chabafie. 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 shock occasioned by the overthrow of our previous associations and preju. dices, we have commonly acceded to them; and almost always, on extending the investigation, we have enjoyed the satisfaction of yielding an unqualified affent.

The innovating hand of M. Haüy has not been confined to these 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 distinguished. Of all the alterations he could possibly devise, this is the one which must prove the most intolerable to veteran mineralogists. It is most offensive to the self-love of many, to the prejudices of others, and to the indolence of all. The discoverers, who have bestowed some favourite denomination on the substance 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 underanother appellation, which, to their ears, must found most barbarous. Those whose attachment to system and establishment renders all innovations suspected and disagreeable, will feel their indignation not a little excited ; and all will find it an unpleasant exertion, to obtain a knowledge of these new names, and to acquire the habit of associating them readily with the objects they represent. Aware, as M. Haüy must have been, of the general disquiet the change of nomenclature could not fail to produce, he ought to have potent arguments to justify his adoption of so unpopular an alteration. Let us examine his inducements.

All All fyftem-mongers seem to be affected by a troublesome propenlity to neology, and have erroneously imagined that there is as much merit in fabricating a word as in discovering a fact. They seem to think that the grandeur and novelty of their language may give an aspect of originality and sublimity to their hypothesis, and that the obscurity in which their phraseology may involve it, will render it more difficult to affail. Frequent failures have not convinced them of the fallacy of these ideas; and almost every theory, from the phlogistic one of Stahl to the tranicendental one of Kant, has been distinguished by an almost entire change in the names of the subjects to which it related. These changes, however, are sometimes necessary; and the old mineralogical nomenclature will be found to contain numerous instances of names that effentially needed reform.

The new chemical nomenclature has been sanctioned by the approbation of all Europe ; and it would be absurd to object to its extension to mineralogy, in every - instance where it could be consistently applied. It is certainly much better to talk of sulphate of barytes, than of ponderous spar; of phosphate of lime, than of apatite ; and of sulphate of strontites, than of schützite, by which the Germans have chosen, with their usual disregard 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. There names can only be disagreeable to those who are ignorant of every thing about a mineral except its mere external appearance, and the appellations by which they have been accustomed to diftin.' guish it; for its chemical name must be suggested by a knowledge of its composition.

As far as the adoption of the chemical nomenclature extends, we most heartily agree, therefore, with M. Haüy's reform ; but there is a very numerous class of minerals composed of earths combined with earths, with or without a metallic oxide, and with or without an alkali. No modifications of language can describe the composition of these substances, without extunding the name to an immeasurable length, and without the greateit confusion, from the similarity of composition in very different minerals. To such substances, therefore, a specific denomination must be applied ; and M. Haüy found to many defects in the old nomenclature, that he has almost entirely changed it.

Where two minerals were associated, in his system, that had formerly been contidered 35 dillinct, it sometimes was requisit, to prevent mistakes, to subititute one new nane in place of the two old ones; and it was absolutely neceflary, when a former D 2

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