Imatges de pàgina

has reduced to the same species bodies arranged in molecules widely different, and separated those formerly associated without sufficient foundation. In all these instances, as we have already remarked--to adopt his own words-chemical analysis has supported the arrangement of the crystallographer.

Romé de l'Isle, whose work is spoken of by our author with great respect,--and which in truth contains a vast treasure of mineralogical information,-established his species from the forms combined with concomitant hardness and specific gravity; but he stopped at the surface, instead of penetrating the interior mechanism of the structure. He suspected that there were primitive forms, but he did not always ascertain them with accuracy : they are chosen indiscriminately; and many are very distant from the true ones, ascertained by mechanical division. He was embarrassed also in the application of his principle to the secondary forms, which retain no resemblance of the adopted primitive; and, in consequence of this difficulty, he sometimes admits two different primitive forms in each species. On the contrary, by the assistance of our author's theory, we may be certain of disco- ering whether any given form can exist among the varieties of a particular species, or whether it should be excluded from it. What is of more consequence, this naturalist, instead of stopping at the primitive forms themselves, afforded by mechanical division, which are the only data proper to facilitate the applications of his theory, has taken, for the foundation of his species, the elements of the crystallisation; that is, the integrant molecules resulting from the subdivision of the primitive forms, and which often differ from them. It was calculation only-a mean which De l'Isle has not employed-that could establish the specific differences between the molecules of the same genus : such are those between the equilateral triangular prism, and the prism with square bases, in determining the particular relation which exists in each species between the dimensions of the prism that nature employs in the production of crystals which belong to this species.

About the time when M. Hauy published his first essays on the structure of minerals, the Academy of Sciences received a memoir from M. Bergman, in which he proposed the reduction of all the figures of calcareous spar to the primitive rhomboid. He had remarked the position of the nucleus in the dodecaedron with scalene triangular faces, of the variety styled the ' hog's-toothed spar. He considered it as produced by the superposition of planes, which decreased around the primitive rhomboid, in separating from the lateral angles. He even verified this explanation by fracture, which is wholly conformable to nature ; but he stopped short at this first view, and did not think of determining, by the help of calculation,

either the laws of decrease, or the form of the integrant molecules. With respect to the secondary figures, he indulged some hypothetical conjectures, scarcely supported by observation-a remarkable example of the failure of the most acute genius, when not assisted by more rigorous methods of inquiry. By founding crystallography on calculation, M. Hauy has created a science which no fashion can destroy: it rests on a foundation as certain as the Newtonian system of the world ; and has contributed to fill many vacuities in the series, which were apparently wanting in former systems. The reader will find that the author's theory is simple in its method, certain in its principles --resting on facts afforded by undoubted observation and unequivocal evidence. It reposes on this—the existence of a primitive form, the faces of which coincide with the natural joints of crystals; and the whole is supported so far by the nature of every known mineral. It is indeed so well founded and supported, that it has often anticipated analysis, and has been supported in turn by chemical investigation. In this work the system is explained in two ways; viz. by reasoning, assisted by figures, which illustrate the progress of the decrease ; 2dly, by analysis, which supposes only a common acquaintance with geometry. Some new geometrical properties are interspersed, which would, independent of mineralogy, interest the geometer.

The species in this work are determined by characters, the most constant and the most unexceptionable, as they are con. nected with the constitution of the integrant molecule. They are of three kinds, viz. physical, geometrical, and chemical. Among the former are, the specific gravity ascertained by Mr. Nicholson's hydrometer, at 14° of Reaumur; hardness, ascertained by the property of scratching a given body; refraction of light, showing objects single or double; electricity, acquired by heat or rubbing ; and phosphorescence, either in consequence of rubbing, or the projection of its powder on hot coals. The geometrical characters are those afforded by a mechanical divisjon, joined to a measure of the angles, which together form the natural joints. The chemical characters are those ascertained by the most simple and easy experiments, with the blow. pipe, acids, or alkalis. **After describing each species in all these views, it is subdivided into varieties, of which some relate to the forms, either regular or undeterminable ; others to the accidents of light,' that is, to the colours and transparency. Each regular form is first represented by a sign composed of letters and ciphers, which show the laws of decrease,' on which the form depends; and next by a figure in projection, which is in some measure a portrait. Each species is also characterised by pointing out the principal angles, in which its relation to the other Varieties consists. The undeterminable forms are distinguished by characters drawn from the most remarkably obvious proper-, ties; and the accidents of light, which constitute the last shade of the picture, are described in general terms, chiefly drawn from familiar language. Each variety of form, whether regular or undeterminable, has its particular appellation; and, by joining this expression with its colour and transparency, the denomination is complete. We regret only that the essential discriminating characters are not retained in a separate section and a more concise appearance.

The analyses are those of Klaproth and Vauquelin; and from these the genera and orders are deduced. Thus each science contributes to the formation of the present system; and to each substance is subjoined its history, the different opinions of mineralogists, the foundation of their mistakes, and the means by which the truth was ascertained. To this the author adds an account of the strata,—though by no means so full and complete as in the work of his successor Brochant, lately alluded to;-as well as the use of each mineral in the arts, in domestic economy, and in medicine. Lapidaries, and those who are fond of the precious stones as ornamental decorations, will in this publication find methods of correcting the ideas usually derived from their colour. He gives an explanation of the different phanomena which depend on philosophical principles; as, the transparency of hydrophanous stones, in consequence of their absorbing water; the beautiful reflected irises of the opal, owing to slight fissures, which interrupt its continuity. The double refraction of the Iceland crystal claims his particular attention, as well as what relates to the electricity of minerals. On the latter subject, the most remarkable circumstances are-1. the different nature of the two electricities, usually situate near the opposite points of the crystal ; 2. the constant relation which exists between the position of these two electricities, and the forms of the body, when regularly crystallised, which derogate from the symmetry so common in the crystals of other substances; from which a method of determining the positions of the two electricities, on inspection of the crystal, will fol. low. Our author adopts the system of M. Coulumb respecting two fluids of this kind, which he thinks will connect all the facts relating to the clectricity of minerals. In this point, however, he is not always successful. On magnetism the author offers some new observations, and has shown that a much greater number of bodies possess polar magnetism than lias hitherto been supposed

The style of this work is peculiarly clear and philosophical: it sometimes rises to a polished elegance, without any affectation of ornament. We mean to return to it, if our other claims will allow: but, lest we should be prevented, or the work be

brought more shall subjos tolerably fully we have

Mineraint and exact,nuscript ; so

brought more directly within the reader's view by an English translation, we shall subjoin our author's arrangement, adding only that his index is tolerably full, which-as we still want a dictionary of mineralogy, a work we have anxiously wished for, and often recommended—is an object of no little conséquence. . Should M. Brochant's treatise have this valuable addition, it will be a publication of the highest importance, as he has annexed the synonyms of various modern authors, scarcely heard of but in Germany. M. Hauy's synonyms are not numerous, but they are select ; and he particularly refers to Bergman, to Kirwan, Romé de l’Isle, and M. Brochant, whose first volume he had seen, while M. Brochant was perusing tho present treatise in manuscript ; so that the references to each áre constant and exact.

Minerals are divided into four classes ; earthy and neutral salts, earths, inflammables, and metals. The orders of the first class are,-1, earthy acidiferous substances; 2. terreous; 3. alkalino-terreous. Of the second class there are no orders or genera. The species follow each other. The reason for the neglect of divisions subordinate to the classes we cannot easily pers ceive : but it may be owing to the obvious nature of many earths which are very different from what they would appear from analysis. Thus some apparently pure clays contain a much larger proportion of silex than of alumine. The third class is divided into simple and compound inflammables. Among the former are sulphur, the diamond, and anthracite ; among the latter amber, jet, and the different coals. The first order of the metallic bodies contains those not immediately oxydable, except with a violent heat, and immediately reducible; the second, those which are more easily oxydable, but immediately reducible; the third, those which are oxydable, and not immediately reducible.

The first appendix contains the substances, whose nature iş not sufficiently ascertained to admit of their arrangement; but among these there are some sufficiently known to be introduced into the former classes, though not yet accurately analysed. The second appendix contains the different aggregates. The first order comprises the 'rocks' of primitive formation; the second, the clays and lime-stones of secondary formation, more evidently from alluvion; the third, the aggregates composed of fragments, as the pudding-stone, &c. The third appendix contains the volcanic products. These are divided into six classes,-1. the lavas; 2. the thermantides, which have the marks of a less intense fire; 3. the products of sublimation ; 4. the decomposed lavas; 5. the tufas; 6. the substances formed subsequent to the melting and cooling, To these are added substances modified by the heat of subterraneous fires, not volcanic. The first class is divided into the stony, the scorified, and the vitreous lavas. The others admit of no subdivision.

A volume of plates is added, containing the representation of the primitive crystals, with the laws of decrease ; to which is prefixed a system of the characters relating to minerals. This may be styled a delineation of a mineral, resembling Linnæus's Delineatio Plantæ, exhibiting a description of the various charac. ters of minerals under distinct heads, with the most striking examples in the mineral kingdom. .

Art. II.- Mémoires Sécrets sur la Russie, &c. Secret Memoirs concerning Russia, and particularly towards the

End of the Reign of Catharine II, and the Beginning of that of Paul I.: forming a Picture of the Manners of Petersburg at the Termination of the Eighteenth Century; and containing a Number of Anecdotes, collected during a Residence of ten Years, &c. &i, 3 Vols. 8vo. Amsterdam (probably Paris). Imported by De Boffe. 1802.

pas compressed wimali degreeuberance

W E are sufficiently on our guard with respect to the nu, merous pretended memoirs that are printed in the French lan, guage. Of late years, Soulavie and others have published many fictitious pieces, sometimes too largely dilated, and at others even artfully forged. In the publication of memoirs, the pro, duction of the original manuscript ought to be insisted on ; for any man of moderate talents, and a general knowledge of some events and intrigues, might easily contriye what are called memoirs, and give such a colour to his style as to make them pass for genuine,

Impressed with this consideration, we took up the present work with no small degree of distrust, which vanished, after a time, on perceiving the exuberance of singular anecdotes, and the 'knowledge, spirit, and character of the present narrative, which is deeply tinged with an intimate acquaintance with Ruse sia and the events that have recently happened in that extraordinary empire : yet the style is too satirical; and the author, who seems to have been dismissed from the Russian service by Paul, exceeds the severity of Suetonius or Tacitus. His production may indeed be terined historical satire, though he sometimes labours to impart an appearance of candour by inserting a sentence or two of praise. His anecdotes would have borne more weight, if he had dedicated some chapters to an account of the splendid actions of Catharine, and a favorable representation of many events, instead of viewing only their shady side : yet the work has great merit, as forming a striking contrast to those

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