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stances already examined, became the subject of investigation; and the mean result of two analyses gave, in 100 grains of the earth, 48 silica, 18 magnesia, 34 oxide of iron, and 24 oxide of nickel.

When we observe that the three other stones were found to contain the same elements as that just now described, only in somewhat different proportions, we may be excused from detaining the Society with the particulars of their several analyses. Nor shall we here dwell upon Mr. Howard's manner of reconciling his results with those of the Abbé Bachelay and Prof. Barthold, any further than to state, that the inferences drawn are favourable to the supposition, that the stones they examined were of the same nature as those here described.

IV. In this section we collect some of Mr. Howard's principal observations on this curious subject. It must be admitted, that notwithstanding the concurring evidence we have of the fall of some of these substances from the atmosphere, yet the fact itself is so repugnant to what we know as yet of the operations of nature, that we are likely to pause a while before we shall venture to form any decided opinion on the subject. Had the fall of all these stones been attended with meteors, we should naturally combine the two phanomena; and in this case Mr. Howard contends, that as these meteors generally move in a direction nearly horizontal, and probably not very high in the atmosphere, the objection of the stones not striking deeper into the earth, owing to their accelerated velocity, would be obviated. The imperfect knowledge we have of the origin and nature of meteors may likewise be considered as an encouragement for inquiring further into this hypothesis.

Should these masses, after all, turn out to be the effects of some regular and simple operation of nature, it is likely that many more will be found on the surface of the earth, which will become the objects of future inquiry. Meanwhile, Mr. Howard has thought proper to take a comparative view, not only of the masses of what has been denominated Native Iron in South America and Siberia, but also of every other specimen that could be met with in our collections of the substances that came under the same denomination. For a description of these substances, together with various observations thereupon, we are likewise indebted to Count de Bournon, who seems to think, that were the particles of iron and nickel in the stones here examined so numerous as to be in contact with each other, and were the earthy particles interposed between them wholly destroyed, as may happen by a variety of causes, the ferruginous cellular texture that would remain would be very similar to the native iron of Siberia and South America; both which have, moreover, by chemical analysis, been found to contain an ample proportion of nickel. The Count, in describing the Siberian iron, mentions the hard transparent nodules found in the cells of that metal, which bear a great resemblance to the peridot (chrysolite of Werner), the decomposition of which leaves the empty cells which we observe in all the specimens that are brought to us. Mr. Howard, on analysing these transparent nodules,

found them consisting of the same elements as the earthy globules of the stone from Benares.

From a collective view of the contents of this paper, we may now reasonably infer, that all the substances here mentioned, not excepting the native trons from Siberia and South America, and some from Bohemia and Senegal, have a manifest relation with each other. Mr. Howard recapitulates these analogies; and, with a view to the further investigation of the subject, closes his paper with the following queries:-1st. Have not all fallen stones, and what are called Native Irons, the same origin ?—2nd. Are all or any the produce of meteors?—and 3dly. Adverting to the circumstance of the Yorkshire stone having fallen during a serene sky, might not this stone have formed a meteor in regions too elevated to be within the reach of our observation?

Observations on the two lately discovered celestial Bodies. By William Herschel, LL.D. F.R.S. Read May 6, 1802. [Phil. Trans. 1802, p. 213.]

The observations described in the first part of this paper relate to the magnitude, the colour, the disc, and the atmosphere of the two moving stars lately discovered by Mr. Piazzi and Dr. Olbers, to which they have assigned the names of Ceres and Pallas; and also to the question, whether they be attended by any satellites. Their magnitudes were determined by means of a comparison of their reflected images with a lucid spot of a disc micrometer placed at considerable distances. The results of many observations were, that the diameter of Ceres does not subtend an angle of more than 0"-40, or in actual length only 1624 miles; and that the diameter of Pallas can hardly measure more than between 71 and 72 miles. The colour of these bodies was ruddy, and in one instance Pallas was of a dusky white. Their discs were never of a well defined planetary appearance; and as to their atmospheres or comas, the greatest extent of that attending Ceres was in one instance about two diameters beyond its disc; in another instance the whole had a cometary appearance; or when viewed most accurately, it bore a great resemblance to a small, much compressed, but ill-defined planetary nebula. Pallas never exhibited more than a faint haziness. As to satellites, it was inferred previous to the observations, that bodies of such very small dimensions could hardly contain a quantity of matter sufficient for the retention of secondary bodies; and in fact the several appearances that seemed to denote the existence of such attendants, were on more careful inspection found to be fallacious.

In the second part of the paper Dr. Herschel enters into an inquiry concerning the nature of these new stars, particularly as to the question whether they be planets or comets. And in order to proceed upon certain grounds, he previously enumerates certain criteria by which the heavenly bodies may be properly distinguished. These, as to the planets, are seven in number. 1. Those till lately discovered are all

of a considerable size; 2. They move in not very excentric ellipses round the sun; 3. The planes of their orbits do not deviate many degrees from the plane of the earth's orbit; 4. Their motion is direct; 5. They may have satellites or rings; 6. They have an atmosphere of considerable extent, which, however, bears hardly any sensible proportion to their diameters; and lastly, Their orbits are at certain considerable distances from each other.

These characters being next applied to the new stars, we find, in the first place, that as to the magnitude, they can certainly not be classed among planets; since the least of these (Mercury) is no less than 73,839 times larger than Pallas; 2. Their motions may perhaps agree sufficiently; but 3. The planes of the orbits of the new stars appear to deviate so much from that of the earth, that, were they admitted into the number of planets, we should have to extend the zodiac far beyond its present limits; and as it is not improbable that more of these bodies will be hereafter discovered, we shall perhaps end in having no zodiac at all. As to the 4th article, The motion of the new stars appears to be direct, like that of the planets. 5. Besides that no satellites have as yet been discovered belonging to these new stars, it may be inferred à priori that they have not a sufficient mass of matter to retain any. 6. The new stars, with respect to the small comas they exhibit, differ widely from planets, and might rather be classed among the comets, did not other circumstances militate against this opinion; and lastly, The orbits of the new stars are so near each other, that the admitting them as planets would materially affect the general harmony that takes place among the rest. As to their being comets, the five following criteria are here given, by which those desultory bodies have hitherto been distinguished :1. They are generally of a very small size; 2. They move in very excentric ellipses, or apparently parabolic arches round the sun; 3. The direction of their motion is totally undetermined; 4. The planes of their orbits admit of the greatest variety in their situation; and 5. They have atmospheres of very great extent, which show themselves in various forms of tails, comas, haziness, &c. On applying these distinguishing characters to the new stars, we find, that as to size, they might perhaps be classed with comets; but that, as to the nature of the curve in which they move, the direction of their motion, and the planes of their orbits, they deviate still more from comets than they do from planets; and that, as to their atmosphere, though they bear in this respect a greater resemblance to comets than to planets, yet, upon a careful comparison with the appearances of several comets observed of late years, it seems evident that they are not entitled to a place among them; the most considerable of their comas being barely one-fiftieth part of the smallest that has ever been observed to attend a comet.

Thus it appears, that neither the appellation of planet nor comet can be assigned to these newly discovered bodies. And it remains, therefore, to find out some new term by which they may be distinguished. Previously to this, the author thinks it necessary to fix

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upon an accurate definition, with a view to facilitate an appropriate denomination. According to this definition they are "Celestial bodies of a small or a very small size, which move in orbits of no very great excentricity round the sun, the planes of which may be inclined to the ecliptic in any angle whatsoever: their motion may be direct or retrograde; and they may or may not have very considerable atmospheres, or very small comas or nuclei."

Description of the Corundum Stone, and its Varieties, commonly known by the Names of Oriental Ruby, Sapphire, &c.; with Observations on some other Mineral Substances. By the Count de Bournon, F.R.S. Read March 25, 1802. [Phil. Trans. 1802, p. 233.]

In a former paper, printed in the Philosophical Transactions for the year 1798, Count de Bournon gave an analytical description of the crystalline forms of corundum from the East Indies and from China. From a note inserted at the beginning of the present communication, we learn, that the great number of specimens of that substance, since collected from different parts, chiefly of the East, have added so considerably to our knowledge relating to that subject, as to render it necessary not only to correct, but even, in many respects, to alter our opinion concerning it: and that hence, rather than create intricacy by introducing this additional knowledge in the form of a supplement, he had thought it expedient to collect all the information that could be obtained into one point of view, in hopes of delivering, in the present paper, with the addition of a chemical analysis which we are taught to expect from Mr. Chenevix, a complete mineralogical history of this curious substance.

The paper is prefaced by a short historical account of the opinions of former naturalists concerning the corundum stone, and its classification in the mineral system. The first of these, who derived their knowledge chiefly from lapidaries, had no hesitation in placing it among the gems, the hardest of which they distinguished by the epithet Oriental, and subdivided them according to their colours. Romé de Lisle was the first who deduced distinctive characters from the crystalline forms of the different sorts, rejecting the colour as a fallacious character. The first chemists who undertook to analyse this stone, thought themselves authorized to consider it as consisting of new elementary earths; but afterwards it was thought, and it appears now with much reason, to belong to the class of those stones which are chiefly, if not entirely, composed of argill. Werner at length also undertook the analysis; but he retrograded somewhat from what has been since found to be the truth, by placing it between pitch-stone and felspar. Abbé Hauy at length, recurring again to the crystalline form, placed it immediately after felspar, and before the Ceylonite; from both which, however, it differs widely, both by its hardness and specific gravity.

We are greatly indebted to the zeal and perseverance of our honourable member, Mr. Charles Greville, for a very ample collec

tion of specimens of this stone, and of various other species which were long thought analogous, but are now found to constitute with it a genus of some extent. This substance, we are now told, presents itself to our senses, especially to our sight, under two very dissimilar appearances. The first is the original corundum imported under that name and also under that of adamantine spar. At times it is brought in irregular fragments, but often in crystals, which are generally of a pretty large size. Those of the other appearance are, in fact, the gems hitherto known by the names of Sapphire, Ruby, &c. Another distinction is next made, according to the texture or fineness of the grain of these stones; the former being called imperfect, and the latter, or the gems, perfect Corundum.

The author now enters into a minute account of the appearances and the principal properties of this substance. And first he treats of its colour. This, he tells us, is at best but an uncertain character in stones, but yet it may at times afford some secondary marks of distinction. The common or imperfect corundum varies, in this respect, according to the country where it is found. That from the Carnatic is of a grayish white, sometimes approaching to a pale green, and sometimes, though rarely, of a red or blue colour: that from China and Ava is generally of a dull green or brown colour; and that from the coast of Malabar appears of a reddish brown.

The perfect corundum which is found in Pegu and in Ceylon is either red, blue, or yellow. The former is the Oriental ruby; the blue is the sapphire; and the yellow the topaz. From a duly proportioned mixture of the blue and the red is produced the purple colour, which constitutes the Oriental amethyst. The union of the blue and yellow forms the green colour, which is proper to the Oriental emerald; and a larger proportion of yellow produces the colour proper to the chrysolite.

2. As to transparency, the crystals of corundum from the Carnatic, having usually rough surfaces, are of course very imperfectly diaphanous; but when broken, their fragments have generally a certain degree of semi-transparency : most of these fragments, when held up to the light, show a number of fissures in their substance, which in a great measure prevent the transmission of light. These fissures arise from a want of cohesion between all the parts of the crystalline laminæ. The red and blue corundum of the Carnatic has a greater degree of transparency than those of any other colour; the blue in particular having generally the preference in this respect.

3. In hardness the corundum comes next to the diamond; but this quality, with regard to intensity, differs greatly, according to the colour and degrees of purity of the specimens. The corundum of the Carnatic, when it is neither blue nor red, is less hard than any other sort; whilst the imperfect blue species exceeds all the other varieties of this kind in hardness,-such is its density that it will emit pretty bright sparks when struck with steel.

4. This substance, like quartz, becomes phosphorescent by collision. The crystals of a red colour, whether of the perfect or im

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