part immediately after the injury presented sharply-defined irregular borders; after six hours the margins were considerably flattened, so that the boundary of the abrasion was much less distinct. After eighteen hours it was difficult to tell the seat of the injury with the naked eye, and its diameter had become reduced to one-half or one-third; and after forty hours recovery was complete. He convinced himself by microscopic investigation that the process of regeneration of the epithelium proceeds from the margins of the abrasion, the layers of cells immediately bounding the seat of injury becoming elongated, and, as it were, sending forth processes towards its centre; so that the margins are rendered very oblique, whilst at the same time the exposed surface of the cornea is raised considerably above the level of that which is still covered by the cells. These views are different, of course, but neither can be yet accepted as conclusive.

A Cheap and Constant Galvanic Battery for Medical Purposes.-Professor A. Hammond describes a battery which has recently been devised for him, in the New York Medical Journal for November. Each cell contains about half-a-gallon of fluid. A disc of sheet copper is laid flat on the bottom of each cell. To the under side of this is affixed a copper wire covered with gutta-percha. The copper sheet forms the negative plate; the insulated wire which rises to the top of the cell is the positive pole. Two or three inches below the upper margin of the cell is suspended by a brass hanger a thick disc-shaped plate of zinc, concave on the lower side, with a round aperture in the centre. This is the positive plate. To this hanger is attached a binding screw, and this forms the negative pole. The body of the battery fluid is formed of a solution of sulphate of zinc. Occasionally, as required, crystals of sulphate of copper are dropped through the central aperture in the zinc to the bottom of the fluid. These dissolve, and produce a layer of blue liquid, which covers the copper. Thus, we have copper in the bottom of the cell, immersed in a solution of copper, zinc suspended above, immersed in a white liquid, the solution of zinc. The mode adopted in other batteries to separate the fluids consists in using a porous diaphragm, or cup, within, and surrounding which are placed dissimilar metals and fluids. The porous septum, it was thought, would allow the current to pass, and yet prevent the admixture of the diverse ele:nents. It has, however, been demonstrated that, when two such liquids, and even two gases, are thus separated, they will invariably become mixed. In this battery, without the intervention of any diaphragm, the denser liquid, the blue, remains in the bottom of the cell, the lighter one overflows and rests upon it; thus arranged, there is less liability to diffusion or mixing than if the two liquids were placed side by side, in vertical columns, with a porous partition between them. The central aperture in the zinc platealso admits the introduction of a hydrometer to measure the density and strength of the liquid. Provision is also made for preventing too rapid evaporation of the fluid. The occasional addition of a little water, and every three or four days dropping in a few crystals of sulphate of copper, is nearly all that is required in the management of this battery.

MINERALOGY, METALLURGY, AND MINING.

The Working of Hamatite Ores.-Among the many papers at the late meeting of the British Association at Edinburgh, was one by Mr. Thomas Ainsworth, on "The Facts developed by the Working of Hæmatite Ores in the Ulverstone and Whitehaven Districts, from 1844-71." He referred first to some correspondence that had taken place between the British Association and the Government on the subject of the investigation of the hæmatite ore-fields. As this had resulted in the investigations being abandoned on the part of the Government Geological Survey, he thought it was the duty of every one who knew anything on the subject to make it public, seeing that when the Bessemer royalty expired—which would shortly be the case this hæmatite would become much more valuable than it was at present. He quite agreed with all that had been done hitherto in this matter, and the facts he was now to present had come under his notice during the last thirty years while residing in Cumberland, near the Ulverstone and Whitehaven districts. Contrary to what had been generally supposed, he had found the hæmatite ore did not confine itself to the neighbourhood of limestone rock, but was to be found in many kinds of rock, and even between two different kinds of rock. He had also found that the hæmatite had some relation to the coal-fields, and was always found in close proximity to these. A peculiarity of the hæmatite ore-fields was that they seemed to run almost exactly from north-west to south-east. Another fact he had discovered was, that carbonic acid was to be found only in very small quantities in hæmatite, while it was found in large quantities in other ironstone. He was aware that hæmatite was to be found also at Haddington and Bristol. The paper was illustrated by several large diagrams.

Ralstonite, a new fluoride, from Arksutz Fiord (U.S.A.).—This is fully described by Mr. George J. Brush, in a recent number of "Silliman's American Journal." It was observed, a few months since, by the Rev. J. Grier Ralston, of Norristown, Pa. Mr. Ralston found a mineral in minute octahedrons associated with thomsenolite, and being unable to identify it, he sent it to Professor Dana, by whom the specimens were passed over to Mr. Brush for examination. The crystals of the new mineral are octahedral; and in some cases they are very minute, but occasionally one to oneand-a-half millimeters in diameter. They are often implanted on the thomsenolite crystals, and also apparently intercrystallised with this species, making it extremely difficult to separate the new mineral sufficiently pure for analysis. The planes of the octahedron are often tinged slightly yellow, and many of them are dull and iridiscent, owing to an excessively thin film of oxide of iron, and hence exact measurement of the inclinations of the faces cannot be made. But they appear to be symmetrical with equilateral faces, and in some cases have all the solid angles replaced by a minute plane.

The Quarterly Metallurgical Report, by David Forbes, F.R.S., is a most useful periodical, and we trust it may receive such support as will induce the proprietors to carry it on. The third number, now before us, is full of important and interesting news from all parts of the Continent and America. Besides, it has just commenced a list of works published in all

languages on the subject of metallurgy and mineralogy, which will make it most valuable to those interested in the subject. We have so high an opinion of this periodical, that we prepare our summary almost altogether from its pages.

Iron and Iron Ores.—A pamphlet has been issued by Dr. Sterry Hunt, F.R.S., entitled "Notes on Iron and Iron Ores," being a report addressed to Sir W. Logan, F.R.S., late director of the survey (published by Dawson Brothers, Montreal, 1870). The contents of this pamphlet are arranged under the following heads:-1. A comparison of the iron ores of Canada with those of Sweden and Norway. 2. Chemical analyses of the Canadian iron ores. 3. Notes on the iron sands of Canada. 4. A sketch of the different methods of making iron and steel direct from the ore. 5. A description of the Ellershausen process for making malleable iron. Some of the facts brought forward by the author specially connected with the Canadian iron manufacture are considered of sufficient interest to warrant their being reproduced in Mr. Forbes's report.

Blast Furnace Sublimates.-A chemical examination of the sublimate or incrustation (Cadmia) which attaches itself to the inside of the upper portion of the lining of the blast furnaces at Stenay (Meuse) has been made by MM. Nivoit and Létrange, whose report, published in the "Annales des Mines," 6, Ser. XXVIII., p. 113, gives its composition as follows:

Phosphorus in Iron and Steel.-According to Salet, the presence of phosphorus in iron and steel may be detected by examining with the spectroscope the flame obtained by burning the hydrogen produced on dissolving the metal in hydrochloric acid.

The Magnet in Practical Mineralogy. For the purpose of separating the magnetic oxide of iron from the magnetic titaniferous iron ore, quartz, &c., which gives so much trouble and expense in working the Canadian iron sands, a simple, ingenious arrangement has been patented by Dr. Larue, of Quebec; in this the ore in the state of sand or powder, is delivered from a hopper, arranged so as to open and close at proper intervals, and to allow the ore to spread in a thin and uniform layer, upon a series of aprons, arranged with interspaces, between two parallel endless bands, which pass over two horizontal cylinders. These aprons, charged with ore, are made, by the movement imparted to one of the cylinders, to pass from beneath the hopper, under a series of permanent horse-shoe magnets, 800 in number, each capable of sustaining about five pounds; arranged upon transverse bars, in five rows of 160 magnets each. Beneath these is a tympan, covered with muslin, which, when the iron ore is passing beneath them, is in contact with the poles of the magnets; as soon, however, as the magnetic portions of the ore have arranged themselves by attraction, in adhesion to the under side of

the tympan, and the apron has moved from beneath, and gone forward to discharge the nonmagnetic portion of the ore at the foot of the machine, the tympan is momentarily withdrawn a short distance from the poles, and the adhering magnetic ore falls in the open space, between two aprons, into a receptacle placed below. This process of loading and unloading the magnets, can be repeated sixty times in each minute.

MICROSCOPY.

The Beading of Diatomacea is well described by Mr. Henry J. Slack, Secretary to the Microscopical Society, in the "Monthly Microscopical Journal." Mr. Slack says that the uniformity of plan in the silicious deposits of diatoms is to a great extent shown, and to a still further extent suggested, by examining one of Möller's admirable" type slides," with a good immersion 4th or higher power. The gradations from large beads distinctly separated, to smaller beads closely approximating, are readily and instructively exhibited, so that it is easy to trace a series, beginning with large forms that present no difficulty of resolution, and concluding with the most delicate that tax the utmost power of the optical apparatus. When beading appears minute under high magnification, and each bead seems in contact with its neighbour, the outline of a section made by a plane passing through the bead rows perpendicular to the uppermost point of their circumference, would exhibit a delicate wavy line, the depressions of which would be extremely small, as they would correspond with the radii of the little spheres, while the width of the curves would correspond with their diameters. All that can be done under these circumstances, by the best adjustments, and the most careful unilateral illumination, is to exhibit minute, and often very faint, alternations of light and shade, indicating rather than demonstratively showing the character of the structure. When the best has been done with any objective, it becomes evident that a slight increase of the difficulty, from greater minuteness of the structure, would render it invisible, and make the surface look plane.

Tolles' Binocular Eye-piece.-Professor Smith has written to the "Monthly Microscopical Journal," explaining that he is not the inventor of this instrument. He exhibited it here, and hence the mistake arose. It is really Mr. Tolles' invention. Mr. Smith says that Dr. Carpenter has made a mistake as to the inventor of it.

An Erecting Mirror, which is made to surmount the eye-piece, has been devised by Mr. C. Richards. It consists of a glass reflector, platinised on the front surface, thus getting rid of the second image, always seen when an ordinary silvered surface is employed. The dissecting needles or knives are not reversed by it, as might have been expected; for after having adjusted the focus, by simply turning the mirror on its axis one quarter from the right hand, the needle held in the right hand is immediately brought into a proper position. The definition or perfection of the image is in no way impaired, and therefore it will be found useful in drawing as well as dissecting. Monthly Microscopical Journal, November.

How to Grind a Diamond to a fine Point for Micro-writing.-This is thus excellently explained in a letter from Mr. Wenham to Mr. Slack, which appears in full in the "Monthly Microscopical Journal." It is briefly as follows:-"A fragment of diamond was imbedded in a short piece of copper wire, 1th in diameter, in the way described in my paper On the Construction of Object-glasses.' This was chucked in the bow lathe or 'jigger,' and another splinter of diamond, similarly mounted, was held against it as a turning tool. Both were, I suppose, about equally ground away, and you could see the dust flying off; in fact, diamonds rubbed together abrade each other just like two pieces of slate pencil will do. It is very easy with a delicate touch at last to bring the rotating diamond to a point as fine as a needle. This is the right thing for glass ruling, and I have no doubt that Nobert uses the same. In Peter's writing machine-turned points are employed, as these only will mark in every direction. At first he used to buy his turned points from the diamond workers at one guinea each, and few of them good even at that. I explained my way of turning the points, at which he succeeded at the first attempt, and ever after that made them with his own hands. He told me afterwards that what before cost him 21s. did not now cost him 18."

Tolles' immersion 1th Object-glass.—In a letter which Mr. Slack received, and which he published in the "Monthly Microscopical Journal" for December, Dr. Woodward says that the Tolles' immersion th, by which the Amphipleura pictures which he sent to the Microscopical Society were made, works either dry or wet, the compensation being effected simply by altering the distance of the front lens from the other two, by means of the screw collar. There is also a low-angle extra front for ordinary work. He finds, with the high-angle fronts, the following measurements:—

objective admirable.

With central light, and on Podura, or anatomical objects, he finds this He wishes he could speak as favourably of Mr. Tolles' higher powers. They are very good indeed, but he has yet to see one of them which will rival the so-called th immersion of Powell and Lealand.

1000

A Machine for Ruling Glass has been devised by Mr. Stanistreet, of Liverpool, and is excellently figured and described in the "Monthly Microscopical Journal" for December. Mr. Slack has given a very full account of it. The machine is constructed for ruling lines from th to theth of an inch apart, and the inventor has added to it the means of further subdivision to the 100th of an inch, but he has not yet been able to procure any diamond fine enough for ruling distinctly more than about 5,000 lines per inch. Mr. Wenham's letter in the preceding paragraph was called out by this

statement.

How to Mount Diatoms.-Readers will study with advantage the following method, described by Capt. Lang, in the "Microscopical Journal" for