Page:Proceedings of the Royal Society of London Vol 1.djvu/102

Rh 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 at- mospheres, or very small comas or nuclei.”

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 com- munication, 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 sub- ject, as to render it necessarynot only to correct, but even, in many respects, to alter our opinion concerning it : and that hence, rather than create intricacy by introdncing 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 com- plete 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 classi- ﬁcation 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 accordinn' 0 their colours. Romé de Lisle was the ﬁrst who deduced distinctive characters from the crystalline forms of the diﬁ'crent 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 mnch 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 collem