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not magnetic. They very much resembled melted sileago, had not be supposed to be derived from impurities in the plumbx, and might their appearance been uniform in the different varieties of that substance, whose analysis has never, I believe, presented any combined silex; and neither good magnifiers, nor friction of the powder between the fingers, could discover the slightest trace of any foreign substance in these specimens. Add to this, in different experiments, I obtained very numerous perfectly black globules on the same pieces which afforded the white ones. In one instance they covered an inch in length, all around; many of them were as large as common shot; and they had all the lustre and brilliancy of the most perfect black enamel. Among them were observed, here and there, globules of the lighter coloured varieties. In one instance the entire end of the parallelopiped of plumbago was occupied by a single black globule. The dark ones were uniformly attracted by the magnet, and I think were rather more sensible to it than the plumbago, which had been ignited, but not melted. We know how easily, in substances containing iron, the magnetic susceptibility is changed by slight variations of temperature. I am aware, however, that the dark globules may contain more iron than the plumbago from which they were derived, as the combustion of part of the carbon may have somewhat diminished the proportion of that substance. I find that the fusion of the plumbago by the compound blow-pipe is by no means difficult: and the instrument being in good order, good results may be anticipated with certainty. As the press is waiting while I write, it is not in my power to determine the nature of all of these various coloured globules, and particularly to ascertain whether the abundant white globules are owing to earths combined with the plumbago, or whether they are a different form of carbon. If the former be true, it proves that no existing analysis of plumbago can be correct, and would still leave the remarkable white fume, so abundantly exhaled between the poles of the deflagrator, and so rapidly transferred from the copper to the zinc pole, entirely unaccounted for. I would add, that for the mere fusion of plumbago, the blowpipe is much preferable to the deflagrator; but a variety of interesting phenomena in relation to both plumbago and charcoal are exhibited by the latter, and not by the former.

A postscript to this communication, dated April 18, gives the following statement:

The anthracite of Rhode-Island is thought to be very pure. Dr. William Meade (see Bruce's Journal, p. 36), estimates its proportion of carbon at ninety-four per cent. This anthracite I have just succeeded in melting by the compound blow-pipe. It gives large brilliant black globules, not attractable by the magnet, but in other respects not to be distinguished from the dark globules of melted plumbago. The experiment was entirely successful in every trial; and the great number of the globules, and their evident flow from, and connexion with, the entire mass, permitted no doubt as to their being really the melted anthracite.

The Kilkenny coal gave only white and transparent globules; but it seems rather difficult to impute this to impurities, since this anthracite is stated to contain ninety-seven per cent. of carbon.

I have exposed a diamond this afternoon to the solar focus in a jar of pure oxygen gas, but observed no signs of fusion, nor indeed did

I expect it, but I wished to compare this old experiment with those related above.

The diamond is now the only substance which has not been perfectly melted.

I inserted a piece of plumbago into a cavity in quick lime, and succeeded in melting it down by the blow-pipe into two or three large globules, adhering into one mass, and occupying the cavity in the lime; these globules were limpid; and nothing remained of the original appearance of the plumbago except a few black points.

The subject is concluded at p. 378, of the Journal, by the additional notice subjoined, dated April 23.

If melted charcoal, plumbago, and anthracite do really approximate towards the character of diamond, we ought to expect that, in consequence of fusion, there would be a diminution of conducting power, with respect both to heat and to electricity. This I find to be the fact. As soon as the point of charcoal is fused by the deflagrator, the power of the instrument is very much impeded by it; but as soon as the melted portion is removed, the remaining charcoal conducts as well as before; and so on, for any number of repetitions of the experiment, with the same pieces of charcoal.

The globules of melted plumbago are absolute non-conductors, as strictly so as the diamond. This fact is very pleasingly exhibited, when a point of prepared charcoal, connected with the zinc pole of the deflagrator, is made to touch a globule of melted plumbago, however small, still adhering to a parallelopiped of plumbago, in its natural state, screwed into the vice connected with the copper pole; not the minutest spark will pass; but if the charcoal point be moved, ever so little aside, so as to touch the plumbago in its common state, or even that which has been ignited, without being fused, a vivid spark will instantly pass. This fact is the more remarkable, because it is equally true of the intensely black globules which are sensibly magnetic, and therefore contain iron, as of the light coloured and limpid ones, which are not attractable.

The globules of melted anthracite are also perfect non-conductors. This may appear the less remarkable, because the anthracite itself is scarcely a conductor; at least, this is the common opinion; and it certainly is strictly true of that of Wilkesbarre and of that of Kilkenny; for when both poles are tipped with those substances, there is only a minute spark, which is but little augmented when charcoal terminates one of the poles. But the fact is remarkably the reverse with the Rhode-Island anthracite; this conducts quite as well as plumbago, and I think even better, giving a very intense light, and bright scintillations. I have now no doubt that the deflagrator will melt it, but have not had time to complete the trial.

If it should be said that the conducting power of the Rhode-Island anthracite may be owing to iron, we are only the more embarrassed to account for the fact, that its black melted globules are insensible to the magnet, and are perfect non-conductors.

It will now probably not be deemed extravagant, if we conclude that our melted carbonaceous substances approximate very nearly to the condition of diamond.

ARTICLE XVI.

NEW SCIENTIFIC BOOKS.

PREPARING FOR PUBLICATION.

Capt. Parry's Journal of a Second Voyage for the Discovery of the North-west Passage. 4to.

Economy of the Eyes, being Precepts for the Improvement and Preservation of the Sight. By W. Kitchener, MD.

Mr. John Curtis has in the press No. I. of his Illustrations of English Insects. We understand the intention of the Author is to publish highly finished figures of such species of insects (with the plants upon which they are found) as constitute the British genera, with accurate representations of the parts on which the characters are founded, and descriptive letter-press to each plate, giving as far as possible the habits and economy of the subjects selected. The work will be published monthly, to commence the 1st of January, 1824.

JUST PUBLISHED.

No. XX. of Sowerby's Genera of Shells, containing Cardita, Cypricardia, Thecidium, Rostellaria, Strombus, and Pteroceras.

Chemical Recreations, a Series of amusing and instructive Experiments, &c. with a Description of a cheap and simple Apparatus.

18mo. 3s.

First Steps to Botany, intended as popular Illustrations of the Science, leading to its Study as a Branch of general Education. By James L. Drummond, MD. 12mo. 100 cuts, 9s.

Lectures on the general Structure of the Human Body, and on the Anatomy and Functions of the Skin. By T. Chevalier, FRS. &c. 8vo. 12s.

The Pupil's Pharmacopoeia. 18mo.

Observations and Commentaries on Medicine compared as a Science with the other learned Professions. By Adam Dods, MD. 8vo. 2s. 6d

ARTICLE XVII.

NEW PATENTS.

J. Christie, of Mark-lane, London, merchant, and T. Harper, of Tamworth, Staffordshire, merchant, for their improved method of combining and using fuel in stoves, furnaces, boilers, and steam-engines.— Oct. 9.

J. R. Cottor, of Castle Magnor, near Mallow, in the county of Cork, for certain improvements on wind musical instruments.-Oct. 9.

J. Henfrey, of Little Henry-street, Waterloo-road, Surrey, engineer, and A. Applegath, of Duke-street, Stamford-street, Blackfriars, Surrey, printer, for certain machinery for casting types.-Oct. 9.

E. S. Swaine, of Bucklersbury, for a method of producing and preserving artificial mineral waters, and for machinery to effect the same. -Oct. 9.

[merged small][merged small][graphic][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][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]

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.

REMARKS.

2. Very foggy morning: fine day. 3. White frost: 4. Cloudy. 5. Rainy. 6. Rainy.

Tenth Month.-1. Rainy.

day fine: evening rainy.

11. Cloudy. 12. Fine.

13. Rainy. 14-17. Fine. 18. Rainy.

7-10. Fine.

19-20. Over

cast. 21-24. Fine. 25-27. Overcast. 28. Fine: rain at night. 29. Fine. 30. Rainy. 31. Rainy: stormy.

RESULTS.

Winds: N, 3; NE, 3; E, 6; SE, 3; SW, 8; W, 4; NW, 3; Var. 1.

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