Page:Proceedings of the Royal Society of London Vol 1.djvu/97

Rh 1788; and the other discovered in Siberia, and described by Pallas. This latter the Tartars consider as a sacred relic which had descended from heaven.

II. For the descriptive part of the four stones which have been analysed by Mr. Howard, we are indebted to the Count de Bournon, who observes in general, that none of them are, or appear ever to have been, of any regular shape; and that when entire they are all coated with a black crust, the thickness of which however is very incon— siderable. The Benares stone being that which has the most striking mineralogical characters, obtained the preference in these descriptions, and served as an object of comparison in the account to be given of the others. The crust already mentioned, which is common to all, is of a deep black colour, and of an uneven surface. It strikes ﬁre with steel, and frequently contains particles of native iron. The stone itself when broken is of a grayish ash-colour, and of a granulated texture: it appears evidently to be composed of four different sub stances; one of them, which is in great abundance, shows itself in the form of small spherical bodies of various sizes, of a gray colour, some- times inclining to brown, perfectly opake, and so hard as to give faint sparks when struck with steel. Another of these substances is a martial pyrites, of a reddish yellow tinge, somewhat inclining to the colour of nickel. When powdered it is of a black colour, and not attractable by the loadstone. The third substance consists of small particles of iron, in a perfect metallic state. These, although they compose only about ﬁth part of the Whole stone, give, however, to the whole mass the property of being attractable by the magnet.

These three substances are united together by means of a fourth as a cement, which is nearly of an earthy consistence, and of a whitish gray. The speciﬁc gravity of the aggregate stone is 3352.

The constituent parts of the stone from Yorkshire are exactly the same as those of the above, except that its is ﬁner, that the globules are more irregular in their shape, that the martial pyrites is in less, and the iron in greater proportion, and that the earthy cement is more compact. Its speciﬁc gravity = 3508.

The Sienna stone was more similar to that from Benares than the last mentioned; the particles of iron were in a somewhat greater proportion. It contained some particles of black oxide of iron; and likewise one single globule of a vitreous substance, of a pale yellow colour inclining to green, and of a hardness rather inferior to that of calcareous spar. The speciﬁc weight of the aggregate was = 3418.

Lastly, the stone from Bohemia was most similar to that from Yorkshire, except that it appeared to be totally free from any par- ticles of pyrites, and on the other hand to have a much larger pro- portion of globules of native iron; many of which, perhaps, on account of the stone having remained longer in the earth, had undergone a degree of oxidation on their surfaces. Its speciﬁc gravity was = 4281.

From these descriptions we learn that these stones, though they have not the smallest analogy with any of the mineral substances already known, have a very peculiar and striking resemblance to each other; a circumstance surely which must excite the attention and