Page:Proceedings of the Royal Society of London Vol 1.djvu/87

Rh self authorized to assert, without hesitation, that radiant light con- sists in undulations of the luminiferous acther. The general infer- ences he draws from his arguments are, that it is clearly granted by Newton that there are undulations, although he denies that they constitute light; and that it being shown in the three ﬁrst corolla- ries of the Eighth Proposition, that all cases of the increase or dimi- nution of light are clearly referable to an increase or diminution of such undulations, and that all the affections to which the undulations would be liable are distinctly visible in the phenomena. of light, it may:therefore be very logically inferred that the undulations are light.

Dr. Young proceeds to attempt the removal of some apparent dif- ﬁculties in the system which he has adopted; and concludes with a summary comparison of light with heat, which he supposes to diﬁ‘er from it only in the magnitude and frequency of its undulations or vibrations.

This substance, which was lately found among the minerals in the British Museum, appears by an entry in Sir Hans Sloane’s Cata- logue, to have been sent to him with various specimens of iron ores, by Mr. Winthrop of Massachusetts, whence it is conjectured that it is the produce of that province. Its resemblance to the Siberian chromate of iron ﬁrst attracted Mr. Hatchett’s notice. It is of a dark brownish gray; its longitudinal fracture is imperfectly lamel- lated, and the cross fracture shows a ﬁne grain. Its lustre isvitre- ous; it is moderately hard, and very brittle.

The analysis was conducted with all the chemical agents usually applied upon those occasions; and the whole process is minutely de- scribed in the paper. From these experiments we learn that this are consists of about one quarter of iron, and three quarters of a sub- stance hitherto unknown, but now proved to be of a metallic nature. both by the coloured precipitate which it forms with prussiate of potash and with tincture of galls, and by the colour which it com- municates to phosphate of ammonia, or rather to concrete phosphoric acid when melted with it.

From the experiments made with the blowpipe, it seems to be one of those metallic substances which retain oxygen with great obstinacy, and are therefore of difﬁcult solution. That it is an acidiﬁable metal appears from the circumstance of the oxide turning litmus paper red. expelling carbonic acid, and forming combinations with the ﬁxed alkalies; but in many points which are enumerated, it ‘is manifestly very different from the acidiﬁable metals hitherto known, "such as arsenic, tungsten, molybdena, and chromium, and it appears to differ still more from the lately discovered metals known by the names of uranium, titanium, and tellurium.