Imágenes de páginas
PDF
EPUB

On communicating a description of the mass to Dr. Hardy, he replied, “I have no doubt that the specimen referred to is the same which I gave Col. Nicholson. It was found at the head of Swanannoah river, near the base of Black mountain, towards the eastern side of Buncombe county.”

The fragment weighs only twenty-one ounces; and, judging from the size and shape of that side which still exhibits the natural outside of the meteor, it is evidently a portion of a mass that must have been much larger. Its texture is throughout, highly crystalline, having all the laminæ (which are unusually thick arranged conformably to the octahedral faces of a single individual. These layers, which commonly have a thickness of one-tenth of an inch, adhere to one another with much tenacity, so as not to be separable by any ordinary force. They manifest a slight tendency however, as the result of weathering, to separate into granular portions of the thickness of the layers themselves; the particles being somewhat oval in form—a result which seems to flow from the existence of very minute veins of magnetic ironpyrites: for when a surface of the iron is polished, it exhibits the appearance of being mapped off into rounded patches by thin veins of the pyrites; and on the application of nitric acid this structure is still farther developed by the corrosion of the veins. Within these areas, the structure of the iron, when etched, scarcely seems crystalline; at most, exhibiting a few faintly marked crossing lines. A somewhat similar structure is visible in the Cocke county iron.

The mass contains several rounded and irregular nodules of plumbaginous matter, (from half to one inch in diameter,) with which again (and often situated in the midst of the kernels) are found large pieces of foliated, magnetic iron-pyrites. In this respect also, the present iron is closely related to the Cocke

county iron.

Its sp. gr.

7.261. It consists of nickel, (with traces of cobalt,)

2.52 Iron,

96-04 Insoluble matter, sulphur and loss,

1:44

100.00 17. Cocke county, Cosby's Creek, Tennessee.—For our earliest notice of this truly wonderful locality of meteoric iron, we are indebted to Dr. Troost, (see Vol. xxxviii, p. 250, 1840,) and for an additional account of its composition by myself, see Vol. xliii, p. 354, (1842.) The history of this locality is still farther illustrated by the following particulars, derived from two letters from Judge Jacob Peck of Jefferson county, Tennessee, the one dated July, 1845, and the other December, of the same year.-Extract from the former, which was addressed to Dr. J. H. Kain of this city: “The large mass of meteoric iron found some years ago in Cocke county, (on a creek called Cosby's,) fell into the hands of some persons who tried to break it with sledge-hammers, but not succeeding, they placed it upon what is here called a log-heap,' where after roasting for some time, it developed certain natural joints, of which advantage was taken with cold chisels and spikes, for its separation into fragments. These were put into a mountain waggon, and transported thirty or forty miles to a sort of forge, and there hammered into 'gun-scalps,' and other articles of more common use. Some remnants of the mass fell into the hands of Dr. Troost. The original mass was one of rare character, and ought to have been preserved entire. Much of it was composed of large and perfect octahedral crystals. Its weight was about a ton. Another mass weighing one hundred and twelve pounds, was found near the locality of the larger one.

This also was malleable, very white, and easily cut with a sharp instrument. It was picked up by a mountaineer, who supposing it to be silver, asked fifteen hundred dollars for it. After retaining it for some years, he finally sold it to a friend of mine for a small sum, who transferred it to Dr. TROost.”

Extract from the letter of December, 1845, to myself: “The weight of the mass has been variously estimated; but I am certain it was never weighed, prior to its being broken up. probably about two thousand pounds. In figure, it was an oblong, square block. I saw several very regular octahedral crystals that had been detached from the exterior angles of the mass. I had formerly supposed that the whole of it had been taken to Lary's forge, in Sevier county, and the greater part of it there wrought into gun-scalps;' but very recently, I have been informed, that part of it was taken to the forge of Peter Brown, in Green county, and there forged. I understand that a man by the name of McCoy, had a neat bar forged from it for making a gunbarrel, which, to use the expression of Brown's son, was as bright as silver.' In the conversation, young Brown informed me that he thought a piece of the iron in its natural state still remained. On searching, it was found by a little girl of the family. It weighs rather more than a pound, and had been preserved by the family as a nut-cracker. *

“The great mass was found on a hill, or rather on an offset of an eminence, at about one hundred feet above the bed of Cosby's creek. I was at the place after the mass was taken away. The formation was a hard clay-slate, and very little impression was left at the spot, except some stains of red oxyd of iron. McCoy,

It was

* This specimen I owe to the kindness of Judge Peck.

who claimed to be the owner of the land, took me there, under the impression that I should be able to aid him in discovering a mine of pure iron near the spot, especially, as the mass of one hundred and twelve pounds was found in the same immediate vicinity. The search of course was to no purpose. The mass of one hundred and twelve pounds appeared to me to be identical in character with the fragments I have seen of that supposed to weigh a ton.”

The sp. gr. of this iron, as given by Partsch, (Die Meteoriten, p. 151,) is 7.26. I have found that of the included magnetic iron-pyrites, to be 4.454.

ORDER THIRD. Brittle.

Section 1st. PURE.

18. Randolph county, North Carolina.—This mass (originally two pounds in weight) was described by me in Vol. xvii

, p. 140, (1830,) as native iron. It had been previously mentioned in Vol. v, p. 262, (1822,) by Prof. D. OLMSTED, in a descriptive catalogue of rocks and minerals collected by him, during his geological survey of North Carolina. It is spoken of by Prof. O., as occurring in the vicinity of a bed of argillaceous iron ore. It is distinctly foliated, the laminæ being thin and much interlaced. Color and lustre resembling those of mispickel. When etched, it presents very fine, almost invisible, feathery lines, much resembling hoar frost on a window pane. Hardness equal to that of the best tempered steel. Sp. gr. = 7:618. The only metal I have been able to detect in this steel, is cobalt, and this only in traces. A reddish brown powder, not soluble in nitro-hydrochloric acid, did not communicate any color to a bead of borax, which led to the suspicion that it was silicon.

19. Bedford county, Pennsylvania.—This variety was described in Vol. xiv, p. 183, (1828,) as native iron, slightly arsenietted. It closely resembles the Randolph county specimen, in structure, color, hardness and lustre. Its sp. gr. = 6.915. In the few grains at my command for its examination, I have been unsuccessful in verifying the existence of arsenic, or of detecting the presence of any other metal, besides iron. Still, its greater analogy to the Randolph iron than to any other terrestrial production, either natural or artificial, induces me to retain it in the category of meteorites.

Section 2d. ALLOYED. 20. Otsego county, New York.—The precise locality of this very curious iron cannot at present be given. It came into my possession under the following circumstances. Two or three persons from Otsego county submitted a number of specimens to Dr. JAMES R. Chilton, practical chemist of New York, for determination, stating that they had collected them in that region. Among the collection was the iron in question, which they described as having been picked up by them in the soil. They were of opinion, that it was some valuable metal ; and were only satisfied that it was iron, by being shown by Dr. C., that it adhered strongly to the magnet. Dr. C. was at once led to suspect that it was a meteoric production, from the peculiarity of its shape; and induced the proprietors to exchange it for several specimens of silver ores, which they were desirous of procuring, to enable them to prosecute their mining researches with more intelligence. By paying Dr. C. the value of the specimens he had given for it, he very kindly transferred it into my hands.

Its weight was 276 grs., and its figure almost spherical or droplike, as represented in the margin. It was covered with a black Fig. 10. coating, save on one side, where it had been partially

polished. The application of a drop of dilute nitric acid to this side, brought into view the most beautiful, raised lines, closely compacted together, and crossing each other in every direction. Its hardness

was too great to allow of its being sawn; it was therefore broken upon an anvil (within a closed ring of iron) by means of heavy blows with a sledge. Its structure within, is foliated, or foliated-columnar, the individuals radiating from the centre to the circumference. Its color when first broken, was a light steel-grey, with a faint yellowish or reddish tinge, somewhat analogous to magnetic iron-pyrites. Interspersed through the mass, a close inspection discovers very minute, perfectly round globules of magnetic iron-pyrites, the number of which is much increased by the aid of the microscope. These globules are easily detached, and leave behind cavities with smooth, silvery colored walls. A polished surface of its interior, on being etched, exhibits a very exquisitely beautiful crystallization, consisting of innumerable, closely compacted, silvery lines, crossing each other in various directions, but rarely forming regular triangles, as in the malleable irons, (but more resembling the brittle irons of North Carolina and Pennsylvania,) more or less spotted with black globules of pyrites.

Being anxious to preserve as much as possible of this smallest of all the known meteoric iron-masses, I have contented myself with such inferences as a solution of less than twenty grains, enabled me to make respecting its composition. It dissolves with difficulty in nitro-hydrochloric acid, at the same time evolving sulphuretted hydrogen, leaving behind minutely divided carbon (plumbago) and a heavy whitish powder. This latter, fused with carbonate of soda on charcoal, gave what appeared to be metallic tin. The clear solution saturated with ammonia, afforded per

oxyd of iron that corresponded to 94:57 per cent. of metallic iron; and the solution possessed an intensely azure blue color, which I ascertained to proceed chiefly from the presence of copper, though nickel and cobalt were also both detected in the liquid. This little meteorite, therefore, contains the following elements :-iron, copper, nickel, cobalt, sulphur, carbon, tin? and possibly chromium.

Notwithstanding this specimen comes from the same county with the Burlington iron, still its peculiar physical and chemical properties, leave no doubt of it having formed a totally independent body; and for aught that yet appears, two hundred and seventy-six grains in weight constitutes the totality of the fall !

APPENDIX TO Class I. a. Grayson county, Virginia.- A meteoric iron is referred to by Prof. J. W. Rogers, as existing in this county, and in which he found 6.15 per cent. of nickel. Vol xliii, p. 169, (1842.)

b. Roanoke county, Virginia.A meteoric iron is mentioned by Prof. W. B. Rogers as existing in Roanoke county, in which he detected the presence of chlorine. Vol. xliii

, p. 169, (1842.) c. Franconia, New Hampshire.— The following note from ROBERT GILMORE, Esq. of Baltimore, leads me to believe that a mass of meteoric iron was obtained by this gentleman, ten or twelve years ago in New Hampshire. “It was supposed by Dr. J. F. Dana (late Prof. of Chemistry in Dartmouth College) to be native iron. I purchased it at a village about twelve miles this side of the notch of the White mountains, of a person who told me, that it was found under the roots of a large tree, which was overturned upon the banks of a small stream in his neighborhood. He informed me that the blacksmith who had tried it, found it to be pure iron, and that he had refused to dispose of it to Dr. Dana, who was desirous of purchasing it. I tempted him, however, by a proposal of a higher offer than he had before had made for it, and obtained the mass. The tree, under whose roots it was found, must have been fifty or one hundred years old. I had presented the mass (whose weight was about fifteen pounds) to the Baltimore Academy of Science, in whose keeping it was lost sight of, during the destruction of their building by fire.”

(To be continued.)

1

« AnteriorContinuar »