ternate change in the direction of the currents were pretty plain. By the introduction of tubes of sulphuric acid, the number of these bands could be reduced to one, and then by continuing the process, the discharge passed into the continuous as before.

Feddersen found that the length of the spark, and the amount of the charge of electricity, had no sensible effect on the duration of a single oscillation; with ten jars of the above mentioned electrical capacity, and a tolerably short metallic circuit, he obtained,

For a 4mm. spark.

Time of one oscl. 0·00000304 sec.

For 8mm. 0.00000305 sec.

With 16 jars and a very long circuit, he obtained,

For a 14mm. spark.

Time of one osel. 0.0000511 sec.

For 9mm. 0.0000514 sec.

The alteration of the area of the electric surface, (number of jars,) exercised an influence according to the law

t=as

t, being the time of a single oscillation; a, a constant, dependent only on the nature of the circuit and the Leyden jars, while s is the number of the jars.

99 1

O. N. R.

12. Interesting Electrical Phenomenon; by C. PIAZZI SMYTH, Astronomer Royal for Scotland.-With reference to the notice on "Photographing Electric Light," on page 272 of the last number of The British Journal of Photography, I beg to send you in a dry-plate picture a similar case which occurred to me on the 21st ult. (July).

I was merely trying the qualities of some newly-prepared dry plates by Mr. Nicol, by taking a window view of house-tops, and was surprised to find every chimney top surmounted by a black streak or brush; i. e., black in the negative, and therefore indicating light. Nothing of the kind was visible to the naked eye in the scene itself, as a really existent fact, nor was any similar appearance visible on the ground-glass of the camera. The appearance, therefore, did not result from any bad action of the lens, which is a very good one. The stop employed was a small one (0.3 inch), and the definition of the developed picture was extremely sharp. Again: the appearance could not be caused by smoke coming from the chimneys, because that would hardly have been luminous; not one-tenth of the whole chimneys could have had fires below them, and either smoke or rarified air would have drifted with the wind, which was blowing sensibly at the time, whilst the dark rays went up. ward straight as arrows. Again: that the chimneys, as chimneys, had nothing to do with it, was shown by a similar brush or ray appearing at the top of a certain little ventilator in the roof of one of the houses shown, and not out of the parts emitting air, but from the ornamental spike at the top.

This circumstance convinced me at the time that the phenomenon was an electrical one, invisible to the eye, but abundantly visible or sensible to the photographic camera, and the occasion was perfectly agreeable thereto; for it was at the conclusion of a week of unusually hot, calm

1 On the action of very weak electric light on the iodized plate, by Prof. O. N. Rood, this Journal, March, 1864, p. 207.

weather, and the sky had that morning become clouded with forms of clouds eminently electrical.

Happily the thunder storm did not break in this neighborhood, being wafted away elsewhere; but had it broken here, the photograph tells exactly where the lightning was preparing to come down; and there is one tall iron chimney in the view, with the strongest ray of the whole above it, showing that that would certainly have been struck in preference to its neighbors, and, if unprovided with metal communication to the earth and water, would infallibly have caused mischief to the house to which it is attached.

I have sent a second plate, taken six days afterward, when east wind and rain had disposed of all the electricity that had been brewing in the air; and it will be seen that, although it is the same view, taken with the same camera, and with the same sort of tannin dry plate, there are no electrical brushes, or black rays, surmounting the chimney pots.-British Journal of Photography.

II. MINERALOGY AND GEOLOGY.

1. On Meteoric Irons; by H. HAIDINGER.-Haidinger presents gocd reasons for considering the metallic iron of Robitzan, another found near Kremnitz in Hungary, and another from the vicinity of Cotta in Saxony, as probably not meteoric.

He next describes a Meteoric iron from Copiapo. Although iron predominates in it, it consists largely of stony material, and is actually a brecciform rock-an agglomeration of fragments, about and in the interstices of which the iron is spread as if it had been introduced in a liquid or pasty state. The stony pieces vary in size from that of a grain of sand to half an inch. Meteoric pyrrhotine (trolite of Haidinger) is mixed with the silicates in pieces sometimes a quarter of an inch in diameter. There is also some graphite. Nickel constitutes 6-4 p. c. of the metallic part.

From the writings of Philippi, Tschudi, and Domeyko, it appears that there are numerous blocks of meteoric iron over the Chilian territory and especially through the desert region of Atacama. Prof. Joy has analyzed one found in the Andes, 50 English miles from Copiapo. His results differ essentially from those obtained by Prof. G. Rose for a meteoric iron from the Sierra of Chaco, sent by Domeyko to the Berlin Museum (Monatsb. Acad. Berlin, Jan. 15, 1864). An abstract of the memoir of Domeyko on the meteoric irons of Chili is given in the Comptes Rendus, March 8, 1863.

The paper takes up next the Iron of Sarepta, Southern Russia. The surface of a plate cut from this iron, examined by reflected light, shows a structure distinctly crystalline-granular, like that of the meteoric iron of Arva (Northern Hungary). An analysis afforded Iron 95.937, schreibersite 1315, tin 0.017, silicium 0.820.—Les Mondes, July 28, 1864, p. 583; from the Ber. Wien. Akad., May 12, 1864.

2. On artificial Anatase, Brookite, and Rutile; by Mr. HAUTEFEUille. -The dry method of forming crystallized titanic acid adopted by Hautefeuille consisted in dissolving the titanic acid in an alkaline fluorid, or in fluorid of calcium, alone or mixed with silica, and submitting the solu

tion to the action of a current of chlorhydric acid gas. As a further perfecting of the method, he makes the vapor of water to react directly on the gaseous fluorid of titanium in a reducing or oxydizing atmosphere.

For Anatase the fluorid of titanium is conducted along a platinum tube to the middle of a second platinum tube in which the vapor of water is passing. The tube is so heated that the fluorid and vapor of water meet at a temperature a little below that of the volatilization of cadmium. Octahedral crystals are formed, having the angles of anatase, and a density between 3.7 and 3.9.

The titanic acid takes the form and angles of Brookite in the presence of fluohydric acid when the temperature at which it is produced is between that required for the volatilization of cadmium and that for zinc. G. 4.1-4.2.

Rutile results when the fluorid of titanium and vapor of water are mixed at a bright red heat. The forms obtained are acicular square prisms with octahedral terminations. G. 4.3.

In these reactions the fluohydric acid acts the same part as the chlorhydric in the method of crystallizing adopted by H. St. Claire Deville; it is an ephemeral solvent of the titanic acid.-Les Mondes, July 28, p. 605. 3. Bishopville meteorite; Chladnite.-The Bishopville meteorite, of which an analysis by Prof. J. Lawrence Smith is given at page 225 of this volume, was chemically investigated by Rammelsberg in 1861 (Monatsber. Berlin. Akad., Sept., 1861, p. 895). He first treated the mass with chlorhydric acid, then with carbonate of soda, and obtained a residue of 90.75 p. c.; and for the part decomposed, the composition Si 2-29, Fe 0-97, Mn 0-20, Mg 3·51, Ča 0·58 = 7·55, besides 0·8 loss by ignition. An analysis of the residue afforded ŝi 60-86, Al 3-00, Fe 0-31, Mg 34-48, Ca 0·11, Na 1·26, K 0·93=100-95. He concludes that in each case the material is only a mechanical mixture and not a chemical compound.

He next divided the powdered stone by elutriation into a lighter (A) and a heavier (B) part, and analyzed them separately, hoping thereby to prove a like, or different, composition for the two. His results are:

Rammelsberg concludes that the so-called chladnite is not a tri-silicate of magnesia, as made by Prof. C. U. Shepard in his analyses, but does not further educe the nature of the species.

Dr. A. Kenngott, in his Uebersicht der Resultate Mineralogischer Forschungen for 1861, published in 1862, cites the above results, and shows, further, that the heavier portion consists mostly of enstatite, the rest including a little olivine, and, as he judges from the alumina found (2.13 p. c.), a few per cent of lime-feldspar, or labradorite. The lighter portion he also makes to consist largely of enstatite, with a little oligoclase.

[The difference between the chemical analyses by Rammelsberg and Smith appears to be owing to the fact that the latter, having a better AM. JOUR. SCI.-SECOND SERIES, VOL. XXXVIII, No. 114.-Nov., 1864.

specimen for examination, separated the pure white chladnite from the mass of the meteorites, as he states in his paper. In consequence of this, Prof. Smith obtained in his carefully made analysis no alumina and no iron, but only the ingredients of a true enstatite, as he himself has announced.-J. D. D.]

4. Crystals of Rhombohedral and Dimetric species often optically biaxial.-BREITHAUPT has published, in Poggendorff's Annalen, cxxi, 326, a notice of the quartz of Euba (near Chemnitz in Saxony), which Prince Salm-Horstmar had found to be optically biaxial (Pogg. Ann., cxx, 334), and in it claims to have first made this observation. It occurs in crystals and also massive. Its hardness is but 6 to 64, and its specific gravity 2-578-2-632. He states that while the plates are distinctly biaxial, there are, as Mr. Jenzsch has shown, both left-handed and right-handed crystals. This quartz weathers with remarkable readiness, although, according to a chemical examination by Reich, it contains no impurity except about per cent of oxyd of iron. It occurs in four narrow veins (1 in. to 2 ft. thick), associated with a feldspar which Breithaupt proposes to describe under the name of paradorite,-a mineral which he had hitherto found only in tin-veins, and which, even in the Euba veins, afforded some tin ore on pulverization and washing. These tin-bearing veins of Euba occur in the Permian red sandstone (Rothliegende).

Breithaupt observes also that chalcophyllite, most apatite and calcite, mimetene, phenacite, dioptase, nepheline, zincite, greenockite, and other rhombohedral minerals, are optically more or less biaxial; and that the same biaxial condition characterizes most crystals under the dimetric system examined by him, as, for example, many of scheelite, wulfenite, cerasine, idocrase (especially the manganesian idocrase of St. Marcel in Piedmont), meionite, zircon, mellite, etc., as well as those of apophyllite long since so made known by Brewster.

He also states that a grossular garnet from Siberia is uniaxial along one tetragonal axis, and that the manganesian garnet, of high specific gravity, is optically isotropic.

[These variations from the normal uniaxial condition under the Dimetric and Hexagonal systems, are like the variations from the normal which occur in all physical characters, and they have been to some extent before observed. The amount of variation, which is the point of greatest interest, is not mentioned by Breithaupt.-J. D. D.]

5. Geschichte der Mineralogie von 1650-1860 (History of Mineralogy from 1650 to 1860); by FRANZ VON KOBELL. 704 pp. 8vo, with 50 woodcuts and 1 lithographic table. Munich, 1864: J. G. Cotta.-The science of Mineralogy could not have found a better historian among its living votaries than Prof. von Kobell. He is a man of profound learning -a scholar in every sense of the term (as well as a poet)—an original investigator and a thorough mineralogist. His work is correspondingly philosophical and complete. He divides the period of the history into three sections, the first including the century from 1650 to 1750, when the science existed only in its elements or first beginning; the second, the half century from 1750 to 1800, when it was taking shape, under the combined influences of the progressing sciences of chemistry and crystallography; and the third, the remaining time, from 1800 to 1860.

Under each of these sections, the author takes up separately the physical, chemical, and taxonomic divisions of the science; and under the third, these divisions are further subdivided for separate treatment. The work closes with a history of mineral species, in which the time and author of original discovery, and many additional details, are given.

6. Mineralogische Notizen; by FRIEDRICH HESSENBERG. No. 6 (fünfte Fortsetzung), 42 pp. 4to, with 3 plates. From the Transactions. of the Senckenburg naturf. Gesellschaft at Frankfort, v, 233.-This continuation of Hessenberg's admirable crystallographic papers includes articles on crystals of Hematite, Blende, Malachite, Cassiterite, Sphene, Linarite, and Chalcolite.

7. Note on the volcanic peaks of Cotapaxi and Arequipa; by J. D. DANA. In the sketch of the peak of Cotapaxi published by Humboldt, the slopes, as deduced from its profile or outline, are 52° on the right and 50° on the left. De la Beche copied this figure in his Geological Observer, with the inclination a little more reduced, viz: to 48° and 45°. In photographs of this volcano taken from near La Tacunga, by Camilius Farrand, the average angle on the right is 27° 15', and the steepest 29° 30'; while on the left, the slope is almost uniformly 30° 50'. In another view (see the following figure), from nearly the same direction, but taken from the base of the mountain, the greatest slope of the right out

line in the profile is 32° 50', and that of the left 30° 10', while the average for the former is 30° 45', and that for the latter 26° 45'. Thus the facts are, as the writer has long believed, very widely different from what would be inferred from the published sketches. On account of this belief, he hesitated much before inserting the copy of De la Beche's figure in his Manual of Geology, (fig. 966, p. 686). Having issued that figure, he would now refer the reader to it in order that he may appreciate the contrast between the true slope and its caricature.

Arequipa, seen from the Carmen Alto, as shown by a photograph published at Lima by the "Sociedad Fotografica," has a slope of 32° 50' in its outline or profile on the right side, and 27° 45' on the left side. The slopes of this volcanic peak are therefore very nearly the same with those of Cotapaxi.

An angle of 45° in a volcanic cone (such as Humboldt gave in his views), could have been made only by ejections of cinders; while slopes below 34°, as are these here referred to, may be a result of ejections of tufa, or of alternations of cinders, tufa, and lava.

8. The Dinotherium an Elephantine Marsupial.-In the department of the Haute-Garonne in France, a pelvis of a Dinotherium has been found. It is of immense size, being 18 metres (5 ft. 11 in. English)