10. Scheelite.

I have observed in North Carolina several new localities of this mineral.

a. At the so-called Dutchmen Vein of the Bangle mine property, Cabarras county, it has been met with between 90 and 100 feet depth, associated with pyrites and chalcopyrite in quartz; forming an ore, which contains from 2 to 3 ounces of fine gold in 2000 pounds. Although it is considerably disseminated through the whole mass of ore in fine grains, the largest masses, which I have seen were not over 4ths of an inch in diameter.

No crystals have been noticed, but only granular masses of a pale yellowish brown color, distinctly showing the octahedral cleavage. It contains:

b. Another locality is at the Flowe mine, Mecklenburgh county, N. C., where it is associated with barytes, chaly bite, pyrites, chalcopyrite, wolfram and rhombic tungstate of lime.

Not more than two crystals have been observed; the first being a modification of the octahedron 1, slightly truncated by li It has a yellowish brown color and would, if perfect, have a length of of one inch; the other crystal was about half that size, had a fine orange color and was a combination of the planes and ; it contained a small quantity of tungstate of baryta. Both crystals gave B.B. traces of tin.

11. Rhombic Tungstate of Lime.

Found also at the Flowe Mine.

It has a yellowish and greyish white color, and a vitreous lustre, which is subadamantine on a fresh fracture.

The crystals are small and indistinct, an aggregation of many individuals frequently formed into one crystal; the largest one, which I have seen, but which was very imperfect, was th of an inch long. All crystals contain a nucleus of wolfram. I have noticed the following planes: I, iî, žī, 1 and lì; cleavage could not be observed.

Are these crystals pseudomorphs? I do not believe it, at any rate, they have not the appearance of pseudomorphs. We know that lime is isomorphous with oxyd of iron and manganese, I would therefore suggest that tungstate of lime is dimorphous, and that in this case it is coating a nucleus of (O, WO,, just

Fe

Mn

like a chrome-alum crystal, when placed into a solution of alum,

deposites upon itself a coating of the latter, or in the same manner, in which the green tourmaline, of Chesterfield, Mass., surrounds a nucleus of the red. I do not think that ever anybody considered the green a pseudomorph of the red one?

12. Wolfram.

I have examined the wolfram, which forms the nucleus of the rhombic tungstate of lime.

Only one crystal has been observed yet, which shows the planes 1, ii, ti and 17. Sp. grav. at 25° Cels. =7.496. It contains:

This corresponds with the formula: 4FeO, WO,+MnO, WO ̧.

13. A few observations on the occurrence of Gold.

Much has been said and written about the occurrence of gold in veins and elsewhere and the formation of the same, but comparing the different theories with some very important facts, we are often at a loss to explain the latter satisfactorily, and it seems to me that we know but very little about this difficult subject. Without any intention to discuss the merits of the different theories, I will give in the following a few data, which may help to throw some light on this question.

Gold is frequently found in diorite (in smaller quantities in syenite and granite) and although it is only rarely observed in the massive rocks, I have seen specimens from Honduras, C. A., where it was imbedded in the diorite without any other association. The result of the complete decomposition of the diorite is generally a red clayish soil and this has in the gold region of North Carolina, etc., a high reputation for its richness in gold. It was in the diorite region of Cabarrus County, N. C., where the first large piece of gold was found, weighing twenty-eight pounds. All this soil is more or less auriferous, but containing the gold somewhat concentrated, nearly in the same ratio, in which the lighter particles have been washed away. But not only in this country the diorite has been found to be auriferous, as is proved by the large piece of eighty-six pounds which was found at Alexandrowsk near Miask in Siberia, nine feet below the surface, in diorite.

The gold obtained from the disintegrated diorite is generally smooth and rounded as if it was water-worn. This cannot be, however, because it lies still in its original, but only altered matrix, and has not been subjected to any attrition by water and

sand; besides, if we observe any cavities in such gold, we find the sharp edges of crystals, etc., in the same, rounded in a similar manner, just as if the whole piece had been subjected to the action of acids, which in reality seems to have been the case. I believe that this is the most natural explanation, because it tells us at the same time, to what source we must trace the gold, which we find in the veins passing through these formations.

The greatest difficulty presents itself by inquiring into the nature of the solvent. I do not believe it is very probable that the gold has been carried off as a silicate of gold, or by the action of chlorhydric acid upon the sulphid. What seems to me most reasonable, is that it was dissolved as terchlorid of gold. If we remember, that the decomposition of pyrites, one of the most common accessory constituents of diorite, produces sulphuric acid, which in the presence of the never wanting chlorid of sodium and an higher oxyd of manganese may liberate small quantities of chlorine, the most powerful solvent of gold, we have at least a very plausible explanation.

After penetrating the decomposed diorite the solution of gold, passing down the veins, comes in contact with reducing agents and is reprecipitated again, frequently in crystals or crystalline forms. I shall farther below make a few remarks about the substances which precipitate the gold, in veins as well as in beds.

An almost positive proof that the gold in the veins of the diorite formation originates from the adjoining rocks is the fact that the deeper the diorite is decomposed, the deeper the gold is found in the veins. Many of these veins do not contain any gold at fifty feet depth, and I have known veins, which were rich near the surface, not to contain a trace of gold at thirty-five feet depth. Very few of these veins (if not on high hills) carry any gold below 120 feet depth.

The occurrence of gold in beds in the metamorphic slates at great depth can far more be relied upon; Gold Hill, in Rowan Co. N. C., for instance, is over 600 feet deep and the ore as rich as ever. Although it cannot be denied that the greater portion of the gold in such deposits is as old as the stratum itself, in which it occurs, it is certain that inside of such auriferous strata constant changes are going on, gold dissolved and reprecipitated. We could not account for the crystalline structure of most of the gold in such beds if we would not presume that the freshly precipitated gold deposits frequently upon that already present.

The description of a few specimens in my collection may be interesting, for they prove that the gold must have been in solution.

a. From Whitehall, Spotsylvania Co. Va.,-shows gold associated with tetradymite, limonite and quartz. The gold is crystallized in forms belonging to the rhombohedral system and

showing very distinctly one rhombohedron, scalenohedron and basal plan; it is coating tetradymite and evidently a pseudomorph after it. I have seen other specimens from the same locality, but of inferior value and beauty.

b. The tetradymite from the Tellurium Mine, Fluvanna Co. Va., and the native bismuth from the Peak of the Sorato in Bolivia, S. A., are frequently interlaminated with gold.

I have made some experiments with a solution of terchlorid of gold and tetrady mite and found that the latter precipitates the gold from a dilute solution easily with a smooth and brilliant surface.

c. In the upper portion of the ore bed in the metamorphic slates at Springfield, Carroll county, Md., which, near the surface, consists of magnetite and at a greater depth of chalcopyrite and other ores, sometimes films of native gold have been observed coating the cleavage planes of magnetite. On close examination it can be noticed that below the film of gold the magnetite is oxydized into hydrated sesquioxyd of iron.

d. A very striking occurrence of native gold is, that where it is associated with pyrites. Most of the pyritous gold ores are too poor to form a positive opinion about the form, in which they contain the gold, from observation, and many authors are of opinion that the gold may exist in the form of a sulphid, either by itself or as a sulphosalt. If we take it for granted that the pyrites itself is the result of the reduction of iron-salts and bear in mind that protosalts of iron reduce gold instantaneously, we cannot adopt this opinion. But even if terchlorid of gold should have been precipitated by sulphydric acid, whilst passing through the vein, it could not remain in that state for a long time, because moist tersulphid of gold in the presence of the smallest trace of an acid is easily decomposed into metallic gold and sulphuric acid. Some specimens of auriferous albite from Winter's vein, Calaveras county, California, show beautifully that, wherever there is a crystal of pyrites, small crystals of gold are attached to it, demonstrating, that the sulphate of iron precipitated the gold, previous to its own reduction into pyrites."

All these facts prove that the gold is carried into the veins from the adjoining rocks, and that the opinion, which considers veins the source of the gold of alluvial and diluvial deposits and the soil, is erroneous.

If another proof was wanted to show the fallacy of this idea, it would be the fact that the gold from the soil or alluvial and diluvial deposits, has rarely the same fineness as that from the veins wrought in the immediate neighborhood of the same, the latter being generally less fine. It is impossible therefore that the destruction of a portion of these veins could have furnished the gold of such deposits.

Philadelphia, July 27, 1859.

ART. XXXI.-Notice of a Memoir by M. Jules Marcou, entitled "Dyas and Trias or the New Red Sandstone in Europe, North America and India."* (In a letter from Sir RODERICK I. MURCHISON to the Editors.)

Gentlemen

IN the early part of last winter I read with surprise the following paragraph in a published letter by M. Jules Marcou on American Geology. "I think that the term Permian, at least as given by Murchison for the strata of the government of Perm, a very improper one. There are strong suspicions that Murchigon has put into his Permian a part if not the whole of the Trias, and I am almost certain that if geologists accept the Russian Permian as Murchison has defined it as the type, the Trias will disappear from classification in Asia, Africa, America, and Australia."

Considering this to be a serious charge, I wrote to M. Marcou and begged to know the grounds on which he had made it. As he had never been in Russia, I called his notice to another expression in his own letter on American geology in which he says: "not having visited Kansas or Nebraska I have no decided opinion respecting the geology of those countries; for I profess the doctrine that geologists must see with their own eyes," &c. I further expressed a wish, that M. Marcou had acted on his own doctrine, as respected Russia, before he passed so severe a judgment on the researches of M. de Verneuil, Count Keyserling and myself. The replies sent to me by that gentleman, though very polite, being by no means satisfactory, I stated to him my intention of publishing our correspondence in your journal. But I abstained to do so until M. Marcou had produced a fuller explanation of his views.

After a study of the original work of my friends and self, M. Marcou has at length produced his results in the Bibliothèque Universelle de Genève under the title of which a translation is given at the head of this letter.

Leaving my able contemporaries in America and the Geological Surveyors in India to settle their accounts with M. Marcou, I have requested my coadjutor, M. de Verneuil, to answer this article in the French language. In the mean time I confidently refer the judgment of the value of this critical essay to all geologists who have followed the progress of their science.

All such persons know, and particularly those who have read the new edition of my work on Siluria, that the absolute distinction between the fossils of the Permian group or Dyas of M. Marcou and those of the Trias is much more sharply defined

* Bibliothèque Universelle de Genève, Mai et Juin, 1859.