Dr. Gregory on a volatile Liquid procured from Caoutchouc by Destructive Distillation; with Remarks on some other Mr. J. T. Graves's Explanation of a remarkable Paradox in the Calculus of Functions, noticed by Mr. Babbage .... 334 Mr. J. Saxton on his Magneto-electrical Machine; with Re- marks on Mr. E. M. Clarke's Paper in the preceding Number 360 Mr. W. Hopkins's Reply to Dr. Boase's "Remarks on Mr. Mr. H. F. Ta'bot's Facts relating to Optical Science. No. IV. 401 Mr. R. C. Taylor on the Carboniferous Series of the United Mr. F. O. Ward's Physiological Remarks on certain Muscles of the Upper Extremity, especially on the Pectoralis Major. Mr. J. Tovey's Researches in the Undulatory Theory of Light, Prof. Berzelius on Meteoric Stones. Page 429 Mr. L. Thompson on a new Method of preparing Iodous Acid 442 Mr. J. T. Graves's Explanation of a remarkable Paradox in the Calculus of Functions, noticed by Mr. Babbage.. 443 Dr. J. Inglis on the Conducting Power of lodine for Electricity 450 Rev. J. W. MacGauley's Account and Explanation of some remarkable Results obtained during a Course of ElectroMagnetic Experiments.. On the Art of Glass-Painting Mr N. T. Wetherell's Observations on some of the Fossils of the London Clay, and in particular those Organic Remains which have been recently discovered in the Tunnel for the London and Birmingham Railroad 452 456 462 Mr. G. Rainey's Reply to Dr. Ritchie's Remarks on Mr. 469 Rev. N. J. Callan on a new Galvanic Battery 472 Dr. Dalton's Observations on certain Liquids obtained from 479 SUPPLEMENTARY NUMBER. Dr. Dalton's Observations on certain Liquids obtained from 481 On Voltaic Electricity.... 484 On the Constitution of Bitumens, by M. Boussingault. Proceedings of the Geological Society Artificial Production of Crystallized Minerals. 487 489 537 Direct Demonstration of the Rule for the Multiplication of 540 On the Solubility of Carbonate of Lime, &c., in Hydrochlo- Method of detecting Sulphurous Acid in the Hydrochloric I. A Portrait of the late FRANCIS XAVIER BARON VON ZACH, Director of the Observatory of Seeberg. II. A Plate illustrative of Dr. FALCONER and Capt. CAUTLEY'S Paper on the Sivatherium giganteum, a newly discovered extinct animal, con. necting the Ruminantia with the Pachydermata. III. A Plate illustrative of Mr. J. BISHOP'S Experimental Researches into the Physiology of the Human Voice. IV. A Plate illustrative of Mr. O. WARD'S Physiological Remarks on the Motion of the Arm. FRANCIS XAVIER BARON VON ZACH. Druzer of the lioratory of Seeberg. Editor the Astronomical Correspondence." LONDON AND EDINBURGH PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. [THIRD SERIES.] JULY 1836. I. Facts relating to Optical Science. No. III. By H. F. TALBOT, Esq., F.R.S.* Optical Properties of the Iodide of Mercury. CHEMICAL writers have observed that this substance exhibits remarkable changes of colour. It is orange-red when cold, but becomes yellow when moderately heated. As it grows cold again, the red tint reappears. Sometimes, however, the yellow exhibits more permanency, as has been remarked by Dr. Inglis in his Essay on Iodinet. He says "that the yellow crystals of the biniodide retain that colour for a considerable time, unless suddenly cooled or agitated, when the characteristic crimson tint of the biniodide again appears." Wishing to examine into the cause of these facts, I placed a small portion of the red iodide between two plates of glass, and warmed it over a spirit-lamp. It immediately sublimed into a yellow powder composed of minute crystals. As it cooled, blood-red spots appeared upon the surface of the yellow mass and gradually spread themselves over the whole, with the exception of some portions around the circumference which usually remained yellow. When examined with a microscope this powder presented the curious appearance of Communicated by the Author. Nos. I. and II. of these "Facts" will be found in Lond. and Edinb. Phil. Mag., vol. iv. pp. 112, 289. See the Number for January last, (vol. viii.) p. 18. Third Series. Vol. 9. No. 51. July 1836. B |