a limited extent at least the breaking up of the last. This is what we should naturally expect in an isomorphous mixture, the sulphids not being present in separable grains; but diffused through the mineral in a state of imperfect chemical combination, and thus rendering even a firm silicate exceedingly susceptible of decomposition.

On examining the results of analysis given above it will further appear, in support of the same theory of the constitution of the mineral, that while the proportions of silica, glucina, and even of oxyd of manganese, are very constant, the proportions of the oxyds of zinc and iron vary very considerably; these metals, although in the analyses separated and determined as oxyds, being, in fact, combined to a greater or less extent with sulphur in the different portions of the mass examined. If now we calculate on this view the oxygen ratio of the silicate, deducting of course from the sum of the oxygen of the bases, an amount of oxygen equivalent in each case to the per cent of sulphur found, it appears, taking the mean result, that the sum of the oxygen of the bases is to the sum of the oxygen of the silica as 16 93: 16.81, or very nearly as 1:1. Moreover, if we regard glucina as a sesquioxyd base we shall have for the oxygen ratio between protoxyds, sesquioxyds and silica, the proportion 8.228.71: 16.81 or very nearly as 1:1:2. Again, the amount of sulphur in the metallic sulphids is very nearly onesixth of the amount of oxygen in the silicate; so that for every twelve equivalents of oxygen in the silicate we have one equiv. alent of sulphur in the sulphids. Hence we deduce as the general formula of the mineral

(†Ř, . ‡Be) Si + ‡RS in which R=Fe. Zn, Mn.

The oxygen ratio of the new mineral is the type ratio of the garnet family, and to this family it undoubtedly belongs. Its mineralogical characters would place it intermediate between Willemite and Iron Garnet where by its composition it naturally falls. This relationship appears in the following table; but it is seen much more clearly on comparing the actual specimens:

It is true that Willemite and Garnet belong to different crys talline systems, but the ordinary form of Willemite really ap

proaches very nearly a rhombic dodecahedron, the difference of angle only amounting to 5°, and there is no good reason for attaching a greater significance to this difference of angle between the corresponding forms of allied systems, than is attached to an equal difference between similar forms of the same system. In its peculiar constitution the new mineral is allied to Helvin, although the two species have no outward resemblance. The holohedral character of its crystallization, the very large amount of iron and zinc entering into its composition, its color, luster, hardness, and other physical as well as chemical properties, all distinguish it from Helvin and prove the mineral to be a new species. As such I take great pleasure in giving to it the name of Danalite, after Prof. James D. Dana, of New Haven, a name so honorably associated with American mineralogy.

Small fragments of Danalite are not unfrequently met with in the quarries at Rockport, and small grains of it, as I have already said, are quite generally disseminated through the granite ledges which form the extremity of Cape Ann. But large masses of the mineral have not been obtained for some time, the portion of the rock in which they were found having been long since quarried. The mineral was first supposed by the local collectors to be Rhodonite, and under this name good specimens of Danalite may probably be found in some of the collections of the country. Specimens of the mineral have also been found associated with green feldspar at the railroad cut near Gloucester, Mass. The mineral at this locality is more garnet-like in structure, and contains a considerable amount of alumina associated with the glucina. An analysis of a specimen from this locality gave the following results:

At Gloucester the Danalite is associated with fluor spar, which I have never recognized on the specimens from Rockport, although the granite, in which the mineral is imbedded, has at both localities a similar character. Danalite is also associated at both localities with two very remarkable varieties of lepidolite mica. These have also been analyzed and an account of the investiga. tion will be given in a future paper.

Separation of Sesquioxyd of Iron from Alumina, Glucina, and most of the rare earths.-The method of Mr. H. Sainte-Claire Deville,' referred to in the above paper, is one of the most accurate processes of analytical chemistry, and would probably have been more generally used had it not been supposed that it required a furnace heat and involved the usual accompaniments of furnace work. The simple modification we have introduced is to substitute a tube of platinum for the tube of porcelain, and a Bunsen's blast lamp for the furnace. We use in the process the condenser of a small platinum still; but a smaller tube about 6" long and" in diameter would be better adapted to the purpose, and would serve many other useful ends in the laboratory. In addition to the tube, a small platinum nacelle would be required, as large as the tube will admit and about 1" in length. With such an apparatus the method of conducting the process is as follows: The tube having been mounted horizontally on any convenient stand, one end of it, which is closed by a doubly pierced india rubber cork, is connected on one side with a small hydrogen generator and on the other with a small flask for generating hydrochloric acid gas. To the other end of the tube is fastened by an india rubber connector a small glass adapter, so curved that the end may dip under water. The mixed bases, whose total weight is known, having been placed in the nacelle in a finely pulverized condition, and the nacelle having been introduced into the tube, the heat of a single Bunsen burner is applied, while a gentle current of hydrogen is caused to flow through the apparatus. In the course of half an hour all the oxyd of iron is reduced to the metallic state. The current of hydrogen is then replaced by a much more rapid current of hydrochloric acid gas and the heat of a blast lamp applied. The reduced iron is now rapidly converted into chlorid, which, being volatilized by the heat and carried forward by the current, dissolves in the water. After a few minutes the action ceases, the heat is then withdrawn, and the current of hydrochloric acid gas being again replaced by a current of hydrogen, the apparatus is allowed to cool. The alumina, or whatever earth may be present, is left behind in the nacelle in a perfectly pure condition and can be at once weighed, while the weight of sesquioxyd of iron is known from the loss. If the product is not perfectly white the nacelle should be returned to the tube and the process repeated. The result can be controlled by also weighing the nacelle after the reduction of the iron, but it is not safe to estimate the amount of iron solely from the loss of weight at this time, since a very small error in this determination would cause an important error in the calculated amount

'Annales de Chimie et de Physique, Tome xxxviii,

of sesquioxyd. We give these details not as new, but because we feel assured that with the simple modification here described the process will be found far more expeditious, convenient and satisfactory, than any other process now in use. A small porcelain tube might be used instead of the tube platinum, but this cannot be recommended, as the porcelain is liable to break unless protected, and when properly protected sufficient heat can hardly be obtained without a furnace. The hydrogen gas is best obtained from a small automatic generator, and the hydrochloric acid gas may be generated in a small flask from coarse salt and sulphuric acid, which has been previously diluted with about one-third of its volume of water, and allowed to cool. This mixture when gently heated gives a constant flow of gas, which almost immediately stops when the lamp is withdrawn. Both gases should pass through a wash bottle containing strong sulphuric acid before entering the tube.

ART. XII.-Memorandum of a variable or temporary Star of the Second Magnitude, seen in the Northern Crown, May, 1866; by E. J. FARQUHAR, Assistant Librarian U. S. Patent Office.

WALKING out between eight and nine o'clock in the evening of Saturday, May 12, near Sandy Spring, Montgomery county, Maryland, and looking over the constellations in the east, I was surprised at the appearance-or apparition I may call it-of a star in the Northern Crown which I could not believe I had ever seen there before. Immediately on reaching home I looked up an atlas of the heavens, and found no such star marked upon it. I then walked over to the house of my uncle, Mr. Benjamin Hallowell, who having looked at another map of his own, and found no record of such a star, came out with me to see it. As soon as I had pointed it out to him, he remarked that he had seen it for several, nights, amounting to three weeks, or as he afterwards said, a month, probably ever since the constellation had come within view of a spot where he was accustomed to take an evening walk. He is therefore, so far as I know, the first person who ever saw it. He had remarked it as an unfamiliar star, and supposed it was a planet, without considering whether any planet ever frequented there. He did not think it had changed position at all during the month, but he was inclined to believe it had varied in magnitude from time to time; though on neither of these matters will he speak positively, because he had not given the star any special attention. It appeared to be two-thirds or three-quarters of a degree south of Epsilon Coronæ. It was of a pure, soft white, and twinkled a little. Seen through a telescope that magnifies about forty times,

it showed nothing of the nature of a comet. I thought it grew brighter during that evening, but will not be certain. I believe those who carefully observed its magnitude pronounced it a little brighter than Alphacca, Alpha Coronæ. One observer seemed inclined to question this, but did not profess to be sure of his judgment in that respect. There can be no doubt that during at least part of that night, the stranger star was fully as bright as Alphacca; I think brighter. Sunday morning it did not seem to have changed in luster, but Sunday night it was only of the third magnitude, and since that time it has gradually faded from sight of the naked eye. On Tuesday night it was taken note of at the Washington Observatory, and I suppose it is therefore not necessary for me to carry this memorandum any further.

ART. XIII.-New and Brilliant Variable Star; by B. A. GOULD. (In a letter to the Editors dated Cambridge, June 9, 1866.)

ON Monday evening, May 14, Mr. S. C. Chandler, Jr., of the U. S. Coast Survey, while engaged in observing the magnitudes of fixed stars, by comparison without optical aid, perceived a brilliant star not a degree from & Corone. At 11 P. M. he estimated its light as between that of 8 and y Herculis, rather nearer to the latter; it was decidedly brighter than & Boötis, and at least two-thirds of a magnitude brighter than ẞ or y Corona.

The sky had been obscured for several successive nights, but Mr. Chandler is confident that, three weeks previous (at which date he had examined the region with care), no star of sufficient brilliancy to attract attention was visible in this place.

On the ensuing evening, May 15, at 9 P. M., Mr. Chandler and myself examined the star together, and agreed in regarding its brilliancy as not essentially different from that of 8 Corona or 7 Herculis, and as intermediate between the two. It was very manifestly fainter than & Boötis.

on

The weather precluded further observations until May 19, which evening the star had decreased by considerably more than two magnitudes, and was very near the limit of visibility to the naked eye. It was compared with several neighboring stars of similar brightness in Hercules and Serpens, both at 9h and at 13h; and in the interval between these comparisons it had diminished by not less than a tenth of a magnitude.

On the 20th, it was no longer perceptible by the unaided eye, but was easily seen and compared by means of an opera glass. Subsequent observations have been made by Mr. Chandler and myself on the 24th, 28th, 31st May, and this evening, June 9; these being the only nights when the exceedingly unfavor