Графични страници
PDF файл
ePub

crystallised, and that the many crystals which it presents should not have been noticed. The varieties of forms of cleavelandite are, however, at least as numerous as those of felspar; the crystals are very distinct, of various sizes, but rather large than small; they are very frequently marked parallel to one of the primitive planes, viz. that which is the least easy to obtain by cleavage. Several of the forms greatly resemble some of the varieties of felspar, being composed of the same number of planes disposed in the same manner, and it is only by using the goniometer that the difference can be perceived. Notwithstanding this great analogy, Mr. Levy believes that the forms of the two substances are incompatible. He considers the primitive of felspar to be an oblique rhombic prism, and not a doubly oblique prism, as it had been supposed by Hauy, and he takes for the primitive of cleavelandite a doubly oblique prism. The crystals of cleavelandite are generally white, sometimes yellowish and reddish; they are transparent, sometimes translucent and opaque, and have a certain brilliancy which does not belong to felspar. Both substances are often found upon the same specimen, and sometimes both in large and well defined crystals. The localities of cleavelandite are very numerous, and this substance seems likely to become one of the most important both in mineralogy and geology. All the rocks of which felspar is considered as a component part, must be re-examined to separate those which really contain felspar, from those which contain cleavelandite. The localities derived from Mr. Turner's collection are the following: Dauphiny, St. Gothard, Tyrol, Piedmont, Baveno, Elba, Vesuvius, Saxony, Sweden, Norway, Siberia, Greenland, United States, and Rio di Janiero.*

The finest crystals come from the Tyrol and from St. Gothard. The largest from Siberia, where they are met upon the same specimen with large crystals of reddish felspar, and smoky quartz. The most transparent come from Dauphiny, where they are met in small transparent, brilliant, macled crystals, with chlorite, quartz, and occasionally felspar ditetraèdre. Specimens of this locality are very commonly met with in collections, and the crystals they contain were described by Hauy as felspar quadridécimal. At Baveno, it sometimes forms the guangue of the fine flesh-coloured crystals of felspar. From Greenland there is a lamellar, chatoyante variety which greatly resembles the moon stone. However, the moon stone from Ceylon does not belong to cleavelandite; it gives easily two cleavages at right angles like felspar. The other cleavages Mr. Levy could not obtain, and what is very remarkable, the direction of the lamina which give the beautiful chatoyant reflection of light, corresponds to no cleavage of felspar, nor to any of the secondary planes observed in that substance.

IV. Change of Musket Balls in Shrapnell Shells.

Mr. Faraday states, that "Mr. Marsh, of Woolwich, gave me some musket balls, which had been taken out of Shrapnell shells. The shells had laid in the bottom of ships, and probably had sea water among them. When the bullets are put in, the aperture is merely closed by a common cork. These bullets were variously acted upon: some were affected only superficially, others more deeply, and some were entirely

Mr. Levy proposes soon to publish more minutely the result of his observations; and the exact localities of each specimen will be given.

changed. The substance produced is hard and brittle, it splits on the ball, and presents an appearance like some hard varieties of earthy hæmatite; its colour is brown, becoming, when heated, red; it fuses, on platinum foil, into a yellow flaky substance like litharge. Powdered and boiled in water, no muriatic acid or lead was found in solution. It dissolved in nitric acid without leaving any residuum, and the solution gave very faint indications only of muriatic acid. It is a protoxide of lead, perhaps formed, in some way, by the galvanic action of the iron shell and the leaden ball, assisted, probably, by the sea water. It would be very interesting to know the state of the shells in which a change like this has taken place to any extent; it might have been expected, that as long as any iron remained, the lead would have been preserved in the metallic state."-(Institution Journal, for Oct. 1823.)

V. Action of Gunpowder on Lead.

Mr. Faraday says, that "Mr. Marsh gave me also some balls from cartridges about fifteen years old, and which had probably been in a damp magazine. They were covered with white warty excrescences rising much above the surface of the bullet, and which, when removed, were found to have stood in small pits formed beneath them. These excrescences consist of carbonate of lead, and readily dissolve with effervescence in weak nitric acid, leaving the bullet in the corroded state which their formation has produced. It is evident there must have been a mutual action among the elements of the gunpowder itself, at the same time that it acted on the lead; and it would have been interesting, had the opportunity occurred, to have examined what changes the powder had suffered."-(Ibid.)

VI. Purple Tint of Plate Glass affected by Light.

"It is well known," says Mr. Faraday, "that certain pieces of plate glass acquire, by degrees, a purple tinge, and ultimately become of a comparatively deep colour. The change is known to be gradual, but yet so rapid as easily to be observed in the course of two or three years. Much of the plate glass which was put a few years back into some of the houses in Bridge-street, Blackfriars, though at first colourless, has now acquired a violet or purple colour. Wishing to ascertain whether the sun's rays had any influence in producing this change, the following experiment was made :-' -Three pieces of glass were selected, which were judged capable of exhibiting this change; one of them was of a slight violet tint, the other two purple or pinkish, but the tint scarcely perceptible, except by looking at the edges. They were each broken into two pieces, three of the pieces were then wrapped up in paper, and set aside in a dark place, and the corresponding pieces were exposed to air and sunshine. This was done in January last, and the middle of this month (September), they were examined. The pieces that were put away from light seemed to have undergone no change; those that were exposed to the sunbeams had increased in colour considerably; the two paler ones the most, and that to such a degree, that it would hardly have been supposed they had once formed part of the same pieces of glass as those which had been set aside. Thus it appears that the sun's rays can exert chemical powers even on such a compact body and permanent compound as glass."-(Ibid.)

VII. Test of Platinum.

Prof. Silliman recommends the hydriodic acid, as, the best test for platinum in solution. When dropped into a weak solution, it almost immediately produces a deep wine red, or reddish-brown colour, which by standing grows very intense. It resembles the effect of muriate of tin, but is more sensible. On remaining a day or two, films of platinum were deposited. The hydriodic acid had been prepared, by putting phosphorus to about an equal bulk of iodine, placed under water in a glass tube, so that it remained mixed with acids of phosphorus, and perhaps phosphorus itself. No other metallic solution gave similar results. (Silliman's Journal, vi. 376.)

-

VIII. Westbury Altitude and Azimuth Instrument.

To most of our astronomical readers it is probably known, that on the return of the Westbury circle to London during the last winter, it was found in a state "unfit for any nice astronomical purpose:" it has, however, under the superintendance of Mr. Troughton, undergone a complete repair; to secure the telescope from flexure, its original object glass of 24 inches aperture, and 43 inches focus, has been replaced by one of the like diameter, but whose focal length is 38 inches only; it separates many of the close double stars, shows distinctly the double ring and belts of Saturn, and was made by Mr. Tully. The artist who has had the immediate management of the repairs is Mr. Simms, of Bowman's-buildings, Aldersgate-street, and we are glad to know that an instrument which has rendered such essential service to astronomical science is again fit for immediate use. We quote the inscription it now bears with pleasure. "With this instrument, the work of Edward Troughton, Mr. Pond substantiated the errors of the Greenwich mural quadrant; the observations were made at Westbury, and are recorded in the Philosophical Transactions. The instrument, having suffered from long exposure to the weather, was repaired and redivided for Mr. South, by William Simms, under the direction, and to the satisfaction, of its illustrious maker."-Aug. 10, 1823.

IX. Correctness of Greenwich Observations.

For some time past we have seen with regret the various attempts which have been made by certain closet astronomers to withdraw the confidence of the public from observations made at the Royal Observatory, and we have waited with much anxiety for the period, when their accusations, and still more dangerous insinuations, should be repelled. That time, we rejoice to say, is arrived; a communication has, we understand, been received from Mr. Bessel, acknowledging that his Catalogue of Principal Stars requires a Correction for Instrumental Flexure; thereby admitting the superiority of the Greenwich one. For this distinguished foreign astronomer we entertain the highest respect; but, when his observations differed so seriously with those made at our own great national establishment, we hesitated not which to confide in; and we are glad our confidence has not been misplaced. To such as have most distinguished themselves by their patriotic endeavours to depreciate the labours of their countrymen, we would offer the following advice:-Use your pens less freely; your instru

ments more frequently; give us results from your observatories, rather than surmises from your closets; and, should fresh discordances arise between the observations made at home and abroad, you may, perhaps, in process of time, be called upon to settle the dispute.

X.

ARTICLE XV.

NEW SCIENTIFIC BOOKS.

PREPARING FOR PUBLICATION.

A Treatise on Organic Chemistry, containing the Analyses of Animal and Vegetable Substances; founded on the Work of Prof. Gmelin on the same subject. By Mr. Dunglison, Member of several Learned Societies, Foreign and Domestic, and one of the Editors of the "Medical Repository."

Dr. Henderson's History of Ancient and Modern Wines, in an elegant Quarto Volume, embellished with Vignettes, and other decorative Wood-cuts from the Antique.

A Treatise on Navigation and Nautical Astronomy; adapted to Practice, and to the Purposes of Elementary Instruction. By Mr. Riddle, Master of the Mathematical School, Royal Naval Asylum.

Observations on the Functions of the Digestive Organs, especially those of the Stomach and Liver. By Dr. Prout.

Naval Battles from 1744 to the Peace in 1814. Critically revised and illustrated. By Admiral Ekins.

A Guide to Practical Farriery; containing Hints on the Diseases of Horses and Neat Cattle, with many valuable and original Recipes from the Practice of an eminent Veterinary Surgeon. By Mr. Pursglove, sen.

ARTICLE XVI.

NEW PATENTS.

J. Hughes, Barking, Essex, slopseller, for certain means of securing the bodies of the dead in coffins.-Sept. 11.

H. C. Jennings, Devonshire-street, Marylebone, for an instrument to be affixed to the saddle-tree, by the application and use of which, inconvenience and distress to the horse may be avoided.-Sept. 11.

J. Sprigg, sen. Birmingham, fender-maker, for a certain improvement in the manufacture of grates, fenders, and fire-iron rests. Sept. 11.

T. Wickham, Nottingham, lace-manufacturer, for his improved and prepared rice, rendered applicable for use in all cases in which starch is applied.-Sept. 11.

W. Hase, Saxthorpe, Norfolk, iron-founder, for his method of constructing mills or machines chiefly applicable to prison discipline.— Sept. 11.

[merged small][merged small][graphic][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][ocr errors][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed]

The observations in each line of the table apply to a period of twenty-four hours, beginning at 9 A. M. on the day indicated in the first column. A dash denotes that the result is included in the next following observation.

« ПредишнаНапред »