صور الصفحة
النشر الإلكتروني

Genus 2. Imbedded.
Sp. 1. Mimophyre,- more sandstones and graywackés.

2. Psefite, - some of the old red sandstones.
3. Poudingue, - this appears to comprise a great variety of

rocks-some of them local, and others ap

pertaining to the former. 4. Breccia, - these are to be distinguished by the angularity

of the fragments.

It is abundantly evident that this arrangement is totally unfit for the purposes of geological description; but it is unnecessary to point out the causes, since they must be obvious to the most ignorant of our readers. The respect which we entertain for the author prevents us from noticing more of its defects as a mineralogical arrangement. We cannot either see the necessity or the propriety of the Neology which he has thought fit to adopt; but it is unnecessary to say more on the subject, as this system seems to have attracted little attention, though published in the Annales de Chimie; (from which work we have taken our abstract), as long ago as the year 1813.

The author next in the order of the Essays is De la Métherie; and his arrangement is preceded by a theory, which, as we do not very well understand it, we shall not attempt to analyze.

His system does not admit of a brief analysis, like the former; and moreover it is not deserving of one. We shall content ourselves therefore with a mere sketch of his plan.

It consists of three grand divisions; the aggregate crystallized, imbedded, and agglutinated. The two latter are again divided into primary, secondary, alluvial, and volcanic.

Under the First Division are twelve subdivisions--the quartzose,--argillaceous,—magnesian,-calcareous,--barytic,-strontianic,-zirconic;-glucinic,- gadolinic,- sulfurous,-combustible,-and metallic: all of these being supposed to form so many classes of aggregate rocks; a very latitudinarian use certainly of that term. In some of these subdivisions are to be found, as might be expected, the well known rocks, such as granite, gneiss, &c. in all the diversity of species and varieties; capriciously enough divided, but all apparently described from actual specimens. This is all very well; but they are accompanied by others, which are either accidental mixtures of minerals, and not rocks at all, or, what is worse, are purely imaginary. From this determination to fill up a visionary plan, we have such rocks, for example, as barytes and fluor spar, strontian and galena, emerald and granite, sulphur and gypsum, anthracite and granite, gold and quartz, and so forth. This, we must say, is egregious trifling.

In the Second Division there are the same twelve subdivisions. But here, as might be expected from thus hunting down his system, the author gets into much greater absurdities, attended by no small confusion. The paste of the quartzose subdivision may be either quartzose, or argillaceous, or magnesian, or calcareous, or barytic. Or else it may be Keralic, or Petrosiliceous, or Tefrinic, or Leucostic, or Ophitic, or Variolitic, or Cornean, or a compound of many rocks. The imbedded substance may also consist of any siliceous mineral. So much for the felicity of this arrangement; to say nothing of these unnecessary terms, each of which would require a definition of its own, Let us see the result-the way in which all this order is applied to practice,

Under the Quartzose subdivision stands first the genus Porphyry, containing eleven species, besides varieties: to which are added the Decomposed porphyries, containing, among other matters, the claystore porphyry of Werner, which is certainly not a decomposed rock. Next comes the genus Amygdaloid, comprising however but two of the numerous varieties of this modification; namely, those which contain agates, and those which contain calcareous spar. The remainder appear to have been forgotten. The third genus is Variolite; containing five species, of which one is the orbicular granite of Corsica; another, clay slate, with occasional crystals of hornblende; another, mica slate, with similar crystals. This may be an arrangement in words, but it is surely nothing more. In the fourth genus we find amygdaloidal porphyries, with an imperfect enumeration of varieties under the name of Species.

. After this follows a sort of episodic division, consisting of Porphyroids of primary formation-rocks which do not contain felspar. Such are, quartz and tourmalin, quartz and garnet, quartz and titanite, argillaceous schist and hornblende (the second time), the same and mica, the same and octoedral iron, mica schist and garnet, mica schist and hornblende (again), talc and bitterspar, steatite and tourmalin, chlorite schist and tourmalin, serpentine and oxidulous iron; together with many other similar compounds, all formally displayed under tặe requisite subdivisions, genera, species, and varieties. If this be an arrangement, we know not that any other division than Porphyroids would have been required; as it might, on the same principle, comprise every compound rock; and many things besides.

After all this (and we have been so confused with Divisions

and Subdivisions that the whole plan of the arrangement vanishes from cur eyes), comes a First Section on the Breccias of primary formation ; a second on Poudingues of the same na-, ture, and a third on Grits; – which ends this strange eventful classification. Each of these contains, of course, the faa. vourite twelve subdivisions already enumerated; although the author has been mightily puzzled to fiii them, if we may judge by such ingredients as the following-a strontianic Leccia, a zirconic breccia, a metallic breccia, and so forth. To be sure, he has the candour to acknowledge that some of these, such as a breccia composed of yttria cemented by yttria, or gadolinic yttria,' has never yet been found; and, we may add, never will.

But it is fruitless to examine further into this scene of confusion, which, under all the parade of logical arrangement, describes imaginary substances, and omits existing ones; confusing pretty nearly all the rest in such a manner as almost to dely the powers of analysis. Pinkerton was at least amusing.

The arrangement of Signior Tondi being a geological one, it is necessary to give a somewhat fuller account of it than of the last; and to enumerate the geological distinctions on which he thinks proper to found it.

He divides his rocks into masses, beds, transition rocks, stratified rocks (foetz), alluvial, and volcanic, substances. This distinction is Wernerian, and to a certain degree theoretical ; and, as will be seen, it is productive of no small confusion.

The first class, that of the massive rocks, consists only of granite (that containing mica), which is exclusively called primary.

The next, consisting of bedded racks, contains secondary granite (how is this ascertained ?) as the first species. Subordinate to this are, quartz rock,-graphic granite, -mica,-compact felspar,---and speckstein. Now, quartz rock is found in enormous strata, and is assuredly not subordinate to any granite; graphic granite again is always found in veins; compact felspar occurs either in veins or large nodular masses; and mica is not a rock at all. Here therefore is a geological arrangement, if it can be called such, deficient in the first and essential principle of geological knowledge.

The second species in this class is weiss-stein, which might with more propriety have been placed under the versatile term subordinate; like many others which, with less propriety, have found their way into this convenient repository of ignorance, Gneiss and Syenite are made subordinate to this species; but, inmediately after, gneiss constitutes a species of itself; having, as subordinate to it, hornblende schist, which is very often unconnected with it in any way, and lepidolite, which is not a rock, but a rare and accidental mineral.

Mica schist forms the fourth species, with fluor spar (which also is not a rock) subordinate; and then follows a long list of rocks and minerals subordinate both to gneiss and mica schist, such as, porphyry, garnet, micaceous greenstone, anthracite oxidulous iron, &c.; and this again is followed by substances subordinate to mica schist only; comprising gypsum, disthene, oxidulous iron, and several other metallic minerals. Argillaceous schist (Thoreschiefer) then comes in, we know not well in what capacity, and that is followed by another list of rocks subordinate to granite, gneiss, and clayslate. These are, greenstone, greenstone porphyry, variolites, the orbicular Corsican granite, and green porphyry. This is again followed by another list subordinate to gneiss, mica schist, and clayslate, including magnesian limestone, dolomite, compact talc, talc schist, and pyrites. Many other subordinations follow, such as those which rank under gneiss and clayslate, granite and clayslate, mica slate and clayslate, and clayslate alone. · This system of perpetual subordination in all the modes of refinement, seems indeed a favourite part of the author's plan. The very geological knowledge which it pretends to impart, is more than questionable; but it is, independently of this, evident, that, in thus constructing his classification, he has introduced inextricable confusion, and entirely mistaken the object of a geological arrangement. His method is moreover operose, as well as obscure; since a brief tabular and subsidiary view of the various alternations of his rocks would have conveyed all this knowledge in a far more intelligible form.

The species which follow mica schist, as far as we can make them out in this confused system of tabulation, are, topaz rock, primary limestone, magnesian limestone, siliceous schist, serpentine (which, by the by, is a massive and not a bedded rock), greenstone, oxidulous iron of two kinds, magnetic and micaceous (eisenglunz), disthene, porphyry, oxidulous iron (again), and amygdaloidal greenstone. Some of these have also their satellites or subordinate rocks; and the species porphyry contains further 16 varieties, besides subvarieties; among which are such substances as pearlstone, obsidian, semiopal, breccia and tufo (apparently both of the trap formation), and lastly syenite. This is an arrangement, we will venture to say, which is neither mineralogical nor geological, nor even commonly logical.

The transition class contains, as might be expected, argillaceous schist, greenstone, porphyries, amygdaloids, siliceous schist,

and limestone; besides granite, sandstone, syenite, ironstone and jasper : the usual system of subordinate arrangements being further pursued. But we will not dwell on this class, as it adds to the confusion of its arrangement the additional obscurity arising from the theoretical assumption on which it is founded.

The fourth class comprises the floetz strata of the Wernerian school; and the arrangement, which appears to contain nothing very new, is as follows. Conglomerate, old red sandstone, bituminous marl slate, marl, mountain limestone, Jura limestone (lias), amygdaloidal limestone, gypsum, salt, variegated sandstone, 2d gypsum, shell limestone, calamine! 4th limestone, 3d gypsum, sandstone, chalk. We will not enter into the details of the subordinate substances. As to the geological arrangement, it would not be within the limits of our plan to show its incorrectness; and it has moreover been often before the public in the hands of the servum pecus' who are content to live in a damnable adherence unto authority.'

We are somewhat puzzled about the coal formation, as the author no doubt has himself been. It appears to form a kind of supplement in this class, and contains, if we understand the arrangement aright, three principal species of coal, with varieties, but without subordinate earthy strata, and followed by fifteen more species of rock, including, among various shales and sandstones, cinnabar, hornstone, clay ironstone, lithomaya, marl, porphyry, and Tripole. Surely this is not the arrangement of any series in nature.

The floetz trap' rocks are called independent stratified ; so that it is pretty plain that our author's acquaintance with them is not of a personal nature. They appear also to have been of a very rebellious disposition, since they form another supplement in this class; and, as might be expected, they comprise basalt, greenstone, clinkstone, porphyry, wacké, amygdaloid, and some other matters. They are further followed by another division of rocks which, though they belong to this, occur also in other formations. These are pitchstone, obsidian, semiopal, sandstone, sand, shale, clay, compact limestone, marl, clay ironstone, chromat of iron, anthracite, wood coal, and jet. This is at least sufficiently confused; nor, as it appears to us, does the author appear to have meditated his subject, or to have formed for himself any definite idea of his own views in the promulgation of the arrangement. He has a rival, to be sure, in our own language, who, in this respect, will compete with him for the leaden crown.

This arrangement of Signior Tondi is terminated by the alluvial, volcanic, and pseudo-volcanic, rocks. We might here

« السابقةمتابعة »