Billeder på siden
PDF
ePub

$

ed, cafts some gloss of speciousness over some of his fuppofi: tions. When excavations are made in a mountain, of which the top and fides are of granit, the granit does 'not become more beautiful and solid as we descend deeper, but changes its appearance insensibly, till it is at last loft in a rock of a quartzeous nature. To those who attribute the formation of all granits to water, it is objected that they do but remove the question a little farther back; for it will still be eno quired what agent wrought, and what quarry furnished the fragments which conttitute granit; hence they will be obliged to feek for the origin of the great masses, whence the fragments were detached, since water cannot produce them..

This objection, if it shall be determined on weighing the opposite probabilities, that granits are the product of aqueous cryftallization, will easily be answered; for every discovery of man does but put back the chief question. Religion, not philosophy, unfolds ultimate causes.

This article is animated with all the spirit of Buffon. It Thews that old age has not clouded his imagination nor enfeebled his eloquence.

He next considers fand-stone, which is composed of small grains of quartz joined together by the intervention of water. The cement which connects them may be conveyed in two ways, by water oozing through, or by vapour, thờ' in some of the inftances quoted in support of this assertion, as in thiofe from M. Lassone, the induration feems to have been occasioned by the air and not by the acceffion of any cement. Pure fand-stone confifts of quartz only; the other forts are contaminated by metallic, and still more frequently by calcareous admixtures ; position of the great masses of fand-stone ; remarkable instance of sand, conveyed no doubt in vapour, penetrating through glass ; varieties of fand-stone; different colours it'ailumes ; the newly discovered crystals always contain a great deal of calcareous earth, whence their rhomboidal form; such are the other principal topics difcufled in this chapter, wherein the author may fairly be said to have ftruck entertainment out of Hint.

Clay' and glaise, or impure clay, derive their origin from vitreous substances mollified and attenuated by the action of the moist eleinents. Clay, either in its proper form or that of slate and fchift, ought to be regarded as the first earth : the ftrata that were first depofited by the waters, consist of this earth ; the irregularity of its ftrata are owing to this early origin, for they refted upon the vaults of caverns, which afterwards fell in. The different forts of clay are described, and the causes of the difference affigned. The following obfervation is brought to thew the influence of clayey strata

[ocr errors][ocr errors]

on

[ocr errors]

ca vegetation. “In summers remarkably dry, such as was that of 1778, trees lose almost all their foliage very early in September, in foils of sand, chalk, tufa, and compounds of there, whereas in countries lying upon clay, they preserve their verdure and leaves; it is not even necessary that the claj should be immediately under the vegetable earth, for in my garden, where the mould, which is three or four feet in depth, rests upon a bed of calcareous earth, fifty-four feet thick, the trees were as green after two months of drought as those in the valley ; this happened because tạe lime-stone refting upon clay, allows the watery exhalations to arise thro' its perpendicular fiffure, which exhalations constantly moisten the mould at the surface.”

In the following articles, in which modifications of calcareous earth are described, their origin is imputed to the collected fragments (detrimens) of marine productions. That common but puzzling phænomenon, the presence of pieces and strata of lilex, is thus explained : “ the cretaceous pow . der was mixed with vitreous and sliceous particles, at the time it was transported and deposited by the waters; after the formation of these calcareous strata thus mixed with Siliceous molecules, the water penetrating through them, took

up these particles and deposited them between the strata, where their affinity united them, and where they moulded by the cavities and intervals in the strata.” Calcareous matters, of primary and secondary formation, may be diftinguished by the absence of thells and impressions of shells from the latter, by their position at the foot of the hills of which the ancient beds having been attached by frost and water, have afforded powder and gravel for the currents to carry away and stratify. Three kinds of strata formed at different periods and by different causes are defined ;, 1. The primitive, containing sea-shells. 2. The second, containing river or terrestrial shells, and, 3. those which exhibit no traces of shells, but are formed of the fragments of the two former. By thefe fuppofitions M. de Luc's objections to the origin of calcareous matters, as above affigned, seem to us in a great measure to be removed. Several marks are there given, by which, if they be just, an ancient stratuņı may be easily recognized. We have afterwards an account of those quarries which afford stone, that is liable to receive damage with the cause of this phænomenon, an account of the petrifying juice, which is nothing but very small particles carried by water and deposited in the interstices of the grains, and the different appearances of the beds as they lie higher or lower, with the reasons of the difference. Al alabafter has been formed by depositions of particles carried away

from

E 3

from higher stratà by water ; under this denomination are ranked ofteocalla and incrustations in general. With respect to marbles, '“ all that has been said of primary or secondary lime-ftones may be applied to them; Nature formed them in the same way, she first piled up heaps of thells and madrepores; these the afterwards reduced to sand or gravel

, which were depofited in horizontal beds. They acquired their first degree of confiftence from their mutual attraction, which was afterwards greatly augmented in the lower strata by the infiltration of petrifying juice incefiantly dripping from those placed above. Thus it happened that the hardest lime-ftone as well as marbles always lie lowermoft, and the greater thickness there is of strata above, the denser are those that are fituated below.” Thefe chapters, and the following on gypfum and compounds of calcareous and vitreous earths, abound with new, ingenious, and apparently just observations. A distinction between gypsum and plaister of Paris is founded, with whatever propriety, on the presence of marine and nitrous acids, besides the vitriolic, in the latter Some ex. periments of a M. Nadaulf are quoted, in support of this opinion, but they do not seem to have been fo conducted as that a cautious realoner would venture to deduce a conclufion from them.

Vegetable earth is found in two states, viz. in that of mould and of mud. The ftratum of mould is always thicker in. úneultivated than cultivated spots. This earth produces most regularly shaped fossils, and even the diamond itself. The granular and marshy ores of iron and martial pyrites derive their origin from mud here the author's reasoning is unusually lame and unfatisfactory.

The first volume concludes with the history of pit-coal, which is given at great length as it occupies above a hundred pages. Pit-coal is said to be entirely formed of the folid fragments and liquid oil of vegetables, indurated by the ada mixture of acids. From peat recent and without mixture of bitumen one may proceed to such as is older and bituminous, and from wood converted into coal (charbonnifié) to real coal: confequently coal is nothing but vegetables preserved by bitumen. After having combated the opinions of two French authors, on the origin of coal, M. Buffon proceeds thus, " in order the better to understand the production of coal, and unfold its composition, it is necessary to trace the decay of vegetable substances both in the air and under water: when lying on the ground, they ferment; and if the accumulation be large, they will take fire, and the residuum will be no longer combustible, after this dissipation of the igneous particles. But under water

the

the decomposition is far flower, the fermentation insensible, and the vegetable fubftances will long, perhaps for ever, preserve the combustible principles, which they would soon have lost if they had lain in the air. Peat exhibits this first decomposition of vegetables under water, as it does not in general contain any bitumen and yet will take fire, as also do thofe black shining specimens of foffil wood, which are so decayed as not to be distinguishable, and yet have retained enough of their inflammable principles to burn, but afford no odour of bitumen. But when this wood has been long buried or under water, it becomes bituminous by the combination of acid with its oil. Apd if it happens to be under strata containing pyrites or vitriolic acid, it becomes pyritous, and yields in burning a strong smell of sulphur.

“ If we trace this decay of vegetables upon land, we shall find that plants and tender kinds of wood afford a black mould, juit like that which is often found in their strata above coal-mines; while the harder forts of wood, as oak and beech, retain their folidity, and form strata of fossil wood frequently to be seen over coal-mines. In short, this mould in time becomes mud or vegetable earth, both which, if they decay slowly, will retain part of their combustible principles : the mould, as it is.converted into mud, is turned red or yellow by the dissolution of the iron, which it contains: it also becomes unctuous and ductile in consequence of the developement of its oil; now, all mould as well as mud retain more or less.combustible particles, and what is at this day found in the form of peat, fosfil-wood, and pit-coal, is nothing but ancient strata of trees, mould and mud."

Having in this manner considered the nature of coal, investigated its origin, and at the same time thewn that its formation is pofterior to the existence of vegetables, the author exainines the situation and extent of its veins, and enumerates the places where it is found. He concludes with lonne observations on its uses and preparations.

We have not room, at present, to accompany him through the fecond volume. We have been diffuse in our abridgement of the first, on account of the respect with which all M. Buffon's opinions are received in his own country, where we have no doubt but the present work, like his preceding productions, will become a standard book, to be quoted and commented on by French authors, who fecm in many instances, by a strange infatuation, to prefer his authorityto the proofs of other writers.

The general reflections that have occurred to us during our perufal of the present treatise, must likewise be deferred to a future number.

MONTHLY

E 4

ers.

MONTHLY CATALOGUE.

[For JANUARY 1785.]

MISCELLANEOUS, Art. 14. The Dramatic History of Master Edward, Miss Ann,

and Others, the Extraordinaries of these Times. Collected from Zaphaniel's Original Papers, by George Alexander Stevens, Author of the celebrated Lecture upon Heads. To which are prefixed, Memoirs of the Life of the Author. A new Edition, illuftrated' with Copper-plates, izmo, 4s. Murray. 1785.

It would be inconsistent with the plan of our work to bestow a very large attention upon a performance long since published, and now revived. The perfons alluded to in the title are Mr. Shuter and Miss Nancy Dawson. The reputation of the author is sufficiently known, and he has drawn a numerous train of admir.

While his compofitions bid defiance to all the laws of fyftematical criticism, it is impossible to deny him the praise of humour and originality. To the edition before us is now prefixed a sketch of the history of the author. Art. 15. An authentic Letter from a disconfolate Member of

Parliament to his unfortunate Son, lately convilled of robbing the Poft Office; London. 15. 60. Dodfley. 1784.

The late abuse of franking is exposed in this publication with a good-humoured severity. There is a good deal of wit, much

general, and fome personal satire in this performance ; which, upon the whole, rises above the mediocrity of the general run of such temporary jeux d'esprit. Art. 16. The Spartan Manual, or Tablet of Morality : being

a genuine Collection of the Apophegms, Maxims, and Precepts of the Philosophers, Heroes, and other great and celebrated Characters of Antiquity; under proper Heads. For the Im. provement of Youth, and the promoting of wisdom and virtue,

12mo. Dilly. London. • This little work is published with the view of advancing the inTerests of virtise and morality. Its design, accordingly, is to be

ommended. But its execution is greatly defcctive; and the vanity f the compiler in his introduction does not ferve to impress the readwith

any favourable opinion of him. He conceives too extraagantly of his piece, when he affirms that nothing of the kind

ver poffe fled to high a title to credit and authority. The fentences and maxims he holds out, have no doubt, the fanction of antiqui

But antiquity was not always in the right; and, if he had been reallyl earned, he might, with the greatest ease, have extracted fomething more perfect from the stores of ancient wisdom. Art. 17 Thoughts on the Slavery of the Negroes. 8vo. 6d.

Philips 1784.

This little tract, in which the author very feelingly and ably pleads the cause of the oppressed negroes, appcars to be a short

abridgment

ty

« ForrigeFortsæt »