hemian iron is an alloy, of which nickel forms eighteen parts in the hundred; in the Siberian iron, it forms feventeen; and in the Senegal iron, five or fix. But what is ftill more striking, and tends to place the fimilarity of their origin beyond all doubt, the Siberian mafs is interfperfed with cavities, containing an earthy fubftance of the very fame nature as the earthy cement and globules of the Benares ftone; nay, the proportions of the ingredients, according to Mr Howard's analyfis, are nearly alike, if we except that of the oxide of iron, which is confiderably smaller in the Siberian earth. This curious fact excites the ftrongest prepoffeflion in favour of the idea, that the Siberian iron owes its origin to the fame caufes which formed and projected the different ftones fuppofed to have fallen on the earth; and, coupled with the other details of the analysis, it naturally leads us to conclude, that the maffes of native iron, as they are called, differ in no refpect from the metallic particles, or the alloy of iron and nickel, which conftitute one of the four aggregate parts in every ftone hitherto examined.

It may be remarked, that, excepting the tradition of the Tartars refpecting the fall of the Siberian iron from heaven, no external evidence has been preserved to illustrate the origin of those maffes of native metal which have been analyzed by chemifts. A tolerably authentic teftimony has, however, been lately found, to prove the fall of a fimilar body in the East Indies. Mr Greville has communicated to the Royal Society (Phil. Tranf. 1803, pt. I.), a very interefting document, tranflated from the Emperor Tchangire's Memoirs of his own reign. The Prince relates, that in the year 1620 (of our æra), a violent explosion was heard at a village in the Punjaub, and during the noise, a luminous body fell from above on the earth. That the amnil (or fiscal officer) of the district immediately repaired to the fpot where the body was faid to have fallen, and having found it to be ftill hot and not burnt up, caused it to be dug; when the heat increasing, he at laft came to a lump of iron violently hot; that this was fent to court, where the Emperor had it weighed in his presence, and ordered it to be forged into a fabre, a knife, and a dagger; that the workmen reported it was not malleable, but fhivered under the stroke; and that it required to be mixed up with one third part of common iron, when the mafs was found to make excellent blades. The Royal hiftorian adds, that upon the incident of this iron of lightning being manufactured, a poet presented him with a diftich, purporting that, during his reign, the earth attained order and regularity; that raw iron fell from lightning, and was, by his world-fubduing authority, converted into a dag ger, a knife, and two fabres.'

VOL. III. NO. 6.

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The exact refemblance of the occurrence here related, in all its effential circumftances, to the accounts of fallen ftones formerJy detailed, and the particular obfervation upon the unmalleable nature of the iron, give, it must be confeffed, a very great degree of credibility to the whole narrative, and bestow additional weight on the inference previously drawn from internal evidence, that the folitary maffes of native iron found in different quarters of the globe, have the fame origin with the ftones analyzed by Vauquelin and Howard.

We have now gone through the whole evidence, both with refpect to the circumftances in which thefe fingular bodies are found, the ingredients of which they are compounded, and the outward appearance and ftructure which they exhibit: we are now to confider the inferences refpecting their probable origin, which this mafs of information may warrant us to draw.

Independent of the distinct negative which the external evidence gives to any fuch conclufions, we are fully entitled to deny that thefe bodies are formed in the ground by lightning, or existed previously there, both from their exact refemblance to each other in whatever part of the earth they have been found, and from their containing fubftances nowhere elfe to be met with. It cannot furely be imagined, that exactly in thofe fpots where fire, of some unknown kind, precipitated from an exploded meteor, happened to fall, there fhould exift certain proportions of iron, fulphur, nickel, magnefra and filica, ready to be united by the heat or electricity. Still lefs conceivable is it, that in every such fall of fire, thofe ingredients fhould firft combine, by twos and threes, in the very fame manner, and then that the binary and ternary compounds fhould unite in fimilar aggregates. But, leaft of all is it reasonable to fuppofe, that bodies formed in the earth fhould, upon being dug up, be found enveloped in a crust different from the rest of their fubftance, and bearing evident marks of having undergone the action of heat in contact with the air.

The fame unquestionable refemblance which prevails among all thefe bodies, and, ftill more, the peculiar nature of the pyrites which they contain, prove very clearly that they have not a volcanic origin. Even if fuch an hypothesis were liable to no other objection, it would be inadmiffible on this ground, that we know of no volcano which throws up fo fmall a portion of matter, and fo uniformly of the fame kind. But though we were to admit the existence of this volcano, where must we place it, that its eruptions may extend from Bengal to England, France, Italy, and Bohemia; nay, Siberia to Senegal and South America? And if we are forced to admit the existence of a series of fuch volcanoes, which are known to us only by these peculiar effects of their eruptions, do

from

we

we not acknowledge that we are compelled to imagine a fet of causes, without any other foundation for our belief in them, than our occafion for their affiftance in explaining the phenomenon? In fhort, do we not account for one difficulty, by fancying a greater? But if it is alleged that the ftones come from volcanoes already known, we demand, what volcano exifts in the Peninsula of India, or in England, or in France, or in Bohemia? And if it is faid that these bodies are projected by Hecla, Etna, &c. to all manner of distances, we must afk, whether this is not explaining what is puzzling, by affuming what is impoffible? It is furely much better to reft fatisfied with recording the fact, and leaving it under all its difficulties, than to increase its wonders by the addition of a miracle.

The fame remark may be extended to thofe who have fancied that the constituent parts of the ftones exift in the atmosphere, and are united by the fire of a meteor, or by the electric fluid. We have no right to make any fuch hypothefis. We have never feen iron, filica, &c. in the gazeous ftate. These bodies may, for ought we know, be compounds of oxygen and azote or hydrogen, &c.; but as yet we have no reason to think fo. Befides, he who amufes us with this clumfy and gratuitous explication, will probably account for every other phenomenon by a fimilar procefs of creation: He may, with equal plaufibility, conceive the earth to be formed by a union of burnt gafes, and then cover it with vegetables, and people it with living creatures, by a few more conflagrations and explofions. Such, however, is the theory moft heavily expounded by M. Izarn-fpun, with tiresome and unprofitable induftry, into cobwebs, which touch every fact, without catching it-and enveloped in the mift of general logical pofitions, which faintly conceal the fundamental postulate-an entire act of creation.

From the whole, we may fafely infer, that the bodies in queftion have fallen on the furface of the earth, but that they were not projected by any volcanoes, and that we have no right, from the known laws of nature, to fuppofe that they were formed in the upper regions of the atmofphere. Such a negative conclusion seems all that we are, in the prefent ftate of our knowledge, entitled to draw. But an hypothefis may perhaps fuggeft itfelf, unincumbered by any of the foregoing difficulties, if we attend to the following undoubted truths.

As the attraction of gravitation extends over the whole planetary fyftem, a heavy body, placed at the furface of the Moon, is affected chiefly by two forces; one drawing it towards the centre of the Earth, and another drawing it towards that of the Moon. The latter of thefe forces, however, is beyond all com

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parison greatest at or near the Moon's furface. But as we recede from the Moon, and approach to the Earth, this force decreases, while the other augments; and at one point between the two planets, thefe forces are exactly equal-fo that a heavy body, placed there, muft remain at reft. If, therefore, a body is projected from the Moon towards the Earth, with a force fufficient to carry it beyond this point of equal attraction, it must neceffarily fall on the Earth. Nor would it require a very great impulfe to throw the body within the fphere of the Earth's fuperior attraction. Suppofing the line of projection to be that which joins the centres of the two planets, and fuppofing them to remain at reft; it has been demonftrated, on the Newtonian eftimation of the Moon's mafs, that a force of projection moving the body 12,000 feet in a fecond, would entirely detach it from the Moon, and throw it upon the Earth. This estimate of the Moon's mafs is, however, now admitted to be much greater than the truth; and upon M. De la Place's calculation, it has been shown that a force of little more than one half the above power would be fufficient to produce the effect. A projectile, then, moving from the Moon with a velocity about three times greater than that of a cannon ball, would infallibly reach the Earth; and there can be little doubt that fuch forces are exerted by volcanoes during eruptions, as well as by the production of fteam, from fubterranean heat. We may easily ima gine fuch cause of motion to exift in the Moon, as well as in the Earth. Indeed, feveral obfervations have rendered the existence of volcanoes there extremely probable. In the calculation juft now referred to, we may remark, that no allowance is made for the refiftance of any medium in the place where the motion is generated. In fact, we have every reafon to believe, from optical confiderations, that the Moon has no atmosphere.

A body falling from the Moon upon the Earth, after being impelled by fuch a force as we have been defcribing, would not reach us in lefs than two days and a half. It would enter cur atmosphere with a velocity of nearly 25,000 feet in a second; but the refiftance of the air increafing with the velocity, would foon greatly reduce it, and render it uniform. We remark, however, that all the accounts of fallen ftones agree in attributing to the luminous bodies a rapid motion in the air, and the effects of a very confiderable momentum to the fragments which reach the ground. The oblique direction in which they always fall, muit tend greatly to diminish their penetrating

power.

may

While we are inveftigating the circumstances that render this account of the matter highly probable, we ought not to omit one

confideration,

confideration, which lies wholly in the oppofite fcale. The greater part of these fingular bodies have first appeared in a high state of ignition; and it does not feem eafy to conceive how their paffage through so rare a fluid as the atmosphere could have generated any great degree of heat, with whatever rapidity they may have moved. Viewing as we do, the hypothefis of their lunar origin as by far the most probable in every other respect, we will acknowledge that this circumftance prevents us from adopting it with entire fatisfaction. And while we see so many invincible objections to all the other theories which have been offered for the folution of the difficulty, we must admit that the fuppofition leaft liable to contradiction from the facts, is nevertheless fufficiently exceptionable, on a fingle ground, to warrant us in concluding with the philofophical remark of Vauquelin, Le parti le plus fage qui nous refte à prendre dans cet etat des chofes, c'eft d'avouer franchement, que nous ignorons entiere'ment l'origine de ces pierres, et les caufes qui ont pu les. produire.'

If, however, a more extenfive collection of accurate obfervations, and a greater variety of fpecimens, fhall enable us to reconcile the difcrepancy, and to push ftill farther our inquiries into the nature of the new fubftance, a knowledge of the internal structure of the Moon may be the fplendid reward of our inveftigations. And, while the labours of the Aftronomer and Optician are introducing new worlds to our notice, Chemistry may, during the ninteenth century, as wonderfully augment our acquaintance with their productions and arrangement, as the has already, within a much fhorter period, enlarged our ideas of the planet which we inhabit.

:

ART. XIII. Analytical Inflitutions In Four Books. Originally written in Italian by Donna Maria Gaetana Agnefi, Profeffor of the Mathe maticks and Philofophy in the Univerfity of Bologna. Tranflated into English by the late Rev. John Colfon, M. A. F. R. S. and Lucafian Profeffor of the Mathematicks in the University of Cambridge. Now first printed from the Tranflator's Manufcript, under the infpection of the Rev. John Hellins, B. D. F. R. S. and Vicar of Potter'sPury in Northamptonshire. 2 Vol. 4to. London. 1801. Sold by Wingrave.

A WORK on the moft profound of the mathematical fciences, from the pen of a lady, can hardly fail to be an object of attention. It has indeed been fo among the learned on the con

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