takes somewhat of a yellowish tinge. Salt of phosphorus dissolves it readily, with a residue of silica, to a clear glass, which upon cooling becomes yellower than might be expected from the white color of the mineral. With a little soda it gives a bubbly glass, dark colored externally; upon the addition of more soda it gives an infusible enamel somewhat colored by manganese.

Lieut. Colonel von Jewreinoff has analyzed this substance with great care and accuracy. The most complete analysis of three, all agreeing however closely, gave the following results.

Hence we deduce for the composition of this mineral,

2Ca2 Si+3A12 Si+4H,

the Ca representing or comprising the compound equivalent.

Mn+3Fe+16Ċa.

In accordance with this formula, the result of the analysis would be

2. Mineralogical Notices; by CHARLES UPHAM SHEPARD, M.D. (Communicated for this Journal.)

Tautolite on the north shore of Lake Superior.-This singular, trappean obsidian was presented to me by Mr. Thomas R. Dutton, on his return from a tour of mining explorations on the north shore of Lake Superior. He informed me that it occurs in veins from one to six inches wide, traversing a stratified greenstone or amygdaloid, situated upon Simpson's Island, as well as upon Fluor Island, which is two miles west of St. Ignas. The mineral has a velvet-black color, a subconchoidal fracture, and a shining vitreous lustre. Its Hardness = 6.5...7.0. Gravity 386. It breaks with the greatest facility, being more brittle than obsidian. Before the blowpipe it fuses into a black glass, attracted by the magnet.

It forms in its color and tenacity a striking contrast with the dysclasite, a mineral found on the south side of the lake in connexion with the trap and the copper, in large sized masses of a pure snow white, or pale rose color, specimens of which were two years ago presented to me by Prof. Forrest Shepherd..

Farther account of the Arkansite.-Mr. W. S. Clark, a student in Amherst College, having recently furnished me with a good sized specimen of this mineral, in which it presents itself in very beautiful crystals as well as massive, (the whole resembling a mass of Elba specular iron ore,) I am able to add a few particulars to my first account of the species. The crystals differ considerably in the relative size or development of the planes, from the modifica

tion first described, and besides in presenting the new faces a, which result from the truncation of the acute angles of the pri mary form. The planes M are here better adapted to measurement than in the a first specimens examined, though still obliging us to employ the reflexions of a lamp light in place of the ordinary window bar. The value obtained for M was constantly between 101° and 101° 15', and that for a on a, 123°.

a

M

d

a

M

a

In my first account, I accidentally omitted to give the specific gravity. It is 3.854. This result I have confirmed by fresh trials.

The chemical examination has been so far extended by the present supply of material, as to establish the conclusion that the before discovered titanic acid in it is possessed of those traits which have induced Prof. Rose to distinguish it as an acid of a new metal, called by him Niobium. In a perfectly powdered state, the mineral is decomposed by four hours boiling in concentrated sulphuric acid, its color gradually changing during the digestion from dark ash grey to a pale yellowish white. It was transferred to a Berlin porcelain crucible and ignited. After full ignition for ten minutes, it was removed from the fire, when it was observed that it still emitted fumes of sulphuric acid. On a farther heating however, these fumes ceased to be evolved. It was found to have lost only 1.89 p. c. of its original weight, and to possess a yellow color while hot, which faded out to white on cooling.

A. It was now treated with dilute sulphuric acid and boiled for half an hour; after which the liquid was poured off, and the insoluble matter was again thoroughly heated and weighed. It had lost scarcely more than 1 p. c. by the process. The acid liquid gave with ammonia a slight flocculent precipitate.

B. A portion of the insoluble powder A was fused with three parts of carbonate of soda for half an hour. It melted perfectly, and had on cooling, a faint bluish tinge in spots. Water loosened it from the crucible, but dissolved it only in the slightest portions. On dropping into this solution either hydrochloric or sulphuric acid, a white precipitate was produced, which did not disappear by boiling. The liquid gave with alcoholic solution of nutgalls, a rich red brown or orange precipitate.

* Mr. Clark received his specimen from Dr. Hitchcock, to whom it had been sent by Dr. W. B. Powell, of the Medical College of Memphis, Tenn. Rev. Mr. Beadle, of New Orleans, from whom I obtained my first specimens of Arkansite, informs me that he received them from Dr. Powell, who was the original discov erer of the locality at Magnet Cove.

† This Journal, ii Ser., vol. ii, p. 250.

C. The insoluble matter B (which the water would not dissolve) was rapidly taken up by hydrochloric, as well as by sulphuric acid, and on boiling became troubled. In these solutions also, the nutgalls produced a rich, orange red precipitate.

D. A portion of the powder A was fused with hydrate of potassa in a silver crucible. Water dissolved the mass freely, compared with the fused mass B. On filtering, the solution soon became turbid, (and on standing a few days, a most abundant white precipitate had subsided.) Portions of the liquid gave with either of the acids above mentioned, a copious white precipitate which did not dissolve by boiling. The acid liquors gave with nutgalls, rich orange red precipitates, and with ferrocyanid of potassium a red brown precipitate, which was somewhat diminished by the addition of hydrochloric acid.

E. A somewhat bulky precipitate was left after the affusion of boiling water upon the mass obtained by fusing the powder with potassa. This readily disappeared on being treated with sulphuric acid, though on boiling it became turbid. It was filtered, and subsequently precipitated by a boiling saturated solution of sulphate of potassa. On cooling, the liquor became heavily clouded with a white precipitate, which on boiling cleared up, but returned as it cooled. The white precipitate was separated by a filter, and across this, boiling water was poured, which dissolved out nearly all its contents. From this solution, potassa threw down a bulky precipitate which dissolved in sulphuric acid, which solution was turbid when boiled, and cleared up, to a certain extent, in cooling.

F. The clear sulphate of potassa, solution E, was also precipitated by potassa. The precipitate was ignited, after which it freely dissolved in sulphuric acid, and the solution remained clear on boiling.

My conclusion from the foregoing is, that the Arkansite is a Niobate of yttria and thorina?

Native Platinum in North Carolina.-In November last, I received in a letter from Hon. T. J. Clingman, of Asheville, N. C., a small reniform grain of native platinum, with the following remark." The enclosed metallic grain was given me by a friend, who says it was found among the gold of one of his rockers. It looks like native platinum." Its weight was 2.541 grs. There was no difficulty, by means of its physical and chemical properties, in identifying it with the substance above suggested. Its specific gravity 18. In a subsequent letter dated Jan. 3d, (written before receiving my reply,) Mr. C. adds still farther, “Mr. T. T. Erwin, who presented it to me, says that his overseer, in whose veracity he has the fullest confidence, gave it to him with the gold obtained from the rocker, and that he (Mr. Erwin) does not entertain the smallest doubt of its having been found in his mine in the north part of Rutherford Co. Should it prove to be platinum, it is a matter of interest to me, as the first specimen of that mineral found in the United States."

Fearing however that the grain might have originated in a foreign locality, I addressed particular inquiries to Mr. C. on this head, and received from him the following additional statements." The platinum specimen formerly sent you, was taken from the gold rocker by Mr. Lyon, the overseer of Mr. Erwin. Mr. L. is a man of good character, and all persons who know him entertain no doubt whatever of his hav

ing obtained the specimen as represented. Mr. L. had no suspicion of its being any thing more than silver, which was known to be found with the gold. The place at which he obtained it, was in Rutherford Co., near the line of the new county of McDowell. I would have sent you his certificate, but I had no doubt that other specimens would be found. In fact, almost every miner to whom I described it said, he had seen just such specimens, but they had supposed them to be fragments of steel or iron that had been broken from the edges of the mining tools."* 3. Oxyd of Cobalt with the Brown Hematite Ore of Chester Ridge, Pa., (Proc. Amer. Phil. Soc., Jan., 1846, iv, 239.)—Dr. Boyé exhibited to the Society a specimen of brown hematite ore from Chester Ridge, three-fourths of a mile west of Chester furnace, Huntingdon County, Pa., containing a small quantity of oxyd of cobalt,-the surface of the ore is in some places covered with a thin film of oxyd of cobalt. It also contains a moderate proportion of manganese.

The ore was dissolved in chlorohydric acid, the solution neutralized by ammonia, and then the iron precipitated by boiling after previous dilution with water. The oxyd of cobalt which remained in the solution with the manganese, was discovered both by its reaction in the moist way, and by the blue bead it yielded with salt of phosphorus.

Bismuthic Gold.-In the letter from which the above is extracted, was forwarded to me a few grains, of which the largest weighed only 0-907 gr., of an alloy of bismuth and gold, to which faint traces of mercury were adhering. Concerning their origin, Mr. C. observes, "They were brought to me by a friend, Mr. Willis, under the impression that they might be platinum. They were mixed with the gold of several days work, and I assisted him in picking them out from a parcel that he brought to the bank in this place. They are evidently not grains of platinum."

In structure they are hackly, or sub-fibrous. Hardness2-5...3-0. Gr. == 12-44... 12.9. Color that of palladium. Malleable, but when thinned out under the hammer it becomes brittle. Scarcely acted upon by nitric acid, or by hydrochloric alone; but in the two, slowly dissolves save traces of a heavy white precipitate. Heated before the blowpipe on charcoal, it melts as soon as touched by the flame into a globule which gives off a white smoke, at the same time coloring the support of a bright yellow, while the charcoal remains hot, but turning white, when cold. If allowed to cool, the globule crystallizes beautifully, with a coarsely indented surface, and has its color changed from grayish white to a distinct golden yellow tinge. By continuing the heat, the globule gradually wastes away to less than half its original bulk, crystallizes less distinctly, grows less fusible, and finally it puts on the appearance of pure gold.

The foregoing notice is introduced here in the form of a note, on account of the suspicion entertained that the substance may prove to be only a product of the miner's process of separating his gold by means of amalgamation, instead of being a true mineral production. Dr. Gibbon, the Superintendent of the U. S. Branch Mint at Charlotte, N. C., whose opinion on the subject I solicited, assures me, that bismuth has repeatedly been detected in several of the gold districts of the southern states, and that he thinks the substance in question is probably a natural production. Mr. Clingman also observes in reference to the same point, "It is my opinion that the grains sent to you were in their natural state. I have seen gold coated so as to be blackened by a film of lead supposed to be obtained from the mercury, but it was only superficial and could easily be rubbed off; but the grains sent you were of a steel grey color, and when fractured were seen to have the same color within as externally. Some of them indeed had a color more nearly inclining to yellowish, and yielded slightly before breaking." 36

SECOND SERIES, Vol. IV, No. 11.-Sept., 1847.

4. Note by M. D'Orbigny on the Orbitolina, (mentioned by Mr. Lyell, at p. 186, this volume.)

To C. LYELL, Esq.

Paris, 18th June, 1847.

Dear Sir, I have been long acquainted with the fossil body, which you forwarded to me, and at this moment I am printing in an elementary work, all the mistakes concerning it; it is, in fact, of all genera that perhaps which has been most often misunderstood, and I should call it the greatest culprit in geology. It is a genus nearly allied to Orbitolina, and which I have named, in consequence of this analogy, Orbitoides. It has always been taken for a nummulite, though it differs from it by the most marked characters. I have known many species such as the O. media, papyracea, and that which you have forwarded to me, and which I had designated by the name of Americana. The Orbitoides are found in the cretaceous and tertiary formations, the Nummulina in the tertiary only. Such at least is the result of my numerous investigations on this subject. The species that you have forwarded to me, had been sent me from North America with a great number of tertiary and cretaceous shells; it came to me without any information respecting it, and I am anxious to know where you found it. ALCIDE D'ORBIGNY.

Yours, &c.

5. Observations on the Drift Furrows, Grooves, Scratches, and Polished Surfaces of the Rocks of Lake Superior; by FORREST SHEPHERD, (in a letter to Prof. Silliman.)-I have noticed, both on the northern and southern shores of Lake Superior, innumerable longitudinal furrows, grooves, scratches and also smoothly polished surfaces, upon granite, sienite and greenstone. These grooves run generally in a direction north and south, varying occasionally with slight obliquity. When the surface of the lake is quiet, these marks may be seen at a considerable depth beneath the transparent water corresponding with those seen on the same rocks at the present level of the lake. You may thence ascend upwards on the banks and hills, on the islands and shores of the lake, and by removing the moss and vegetation, you will find these marks continue with remarkable uniformity until you reach the summits of the Huron Mountains, which according to the measurement of Capt. Bayfield, are situated eight hundred feet above the present level of the lake. While standing on the summit of these mountains, in some places I found the compact undecomposed feldspar, as smoothly polished as if it had been soft wood recently subjected to the carpenter's plane or drawing knife; while in other places were to be seen marks and furrows as above mentioned. These appearances, which I have described, are all upon rocks in place, and could not, I think, have resulted from natural structure. Nor could they have resulted from causes now in operation on the shores of this great body of fresh water; for there is no perceptible difference between the marks on the same kind of rock at the present level of the lake, and those at a greater height or lower depth. By enumerating the concentric circles of the largest trees (Pinus abies) which are now standing on the shores of the lake, only three or four feet above the surf, and comparing them with the decayed trunks of similar ones whose stumps have been preserved by having been charred by the fire passing over them, it is perfectly