be, the importance and singularity of the subjects, or the advantageous manner of treating them; without pretending to answer for the certainty of the facts, or propriety of the reasonings, contained in the several papers so published, which must still rest on the credit or judgment of their respective authors. It is likewise necessary on this occasion to remark, that it is an established rule of the Society, to which they will always adhere, never to give their opinion, as a Body, upon any subject, either of Nature or Art, that comes before them. And therefore the thanks which are frequently proposed from the Chair, to be given to the authors of such papers as are read at their accustomed meetings, or to the persons through whose hands they receive them, are to be considered in no other light than as a matter of civility, in return for the respect shewn to the Society by those communications. The like also is to be said with regard to the several projects, inventions, and curiosities of various kinds, which are often exhibited to the Society; the authors whereof, or those who exhibit them, frequently take the liberty, to report, and even to certify in the public newspapers, that they have met with the highest applause and approbation. And therefore it is hoped, that no regard will hereafter be paid to such reports and public notices; which in some instances have been too lightly credited, to the dishonour of the Society. I. ON a new detonating Compound, in a Letter from Sir HUMPHRY IV. Observations relative to the near and distant Sight of different Persons. By James Ware, Esq. F. R. S. V. The Bakerian Lecture. On the elementary Particles of certain Crystals. By William Hyde Wollaston, M. D. Sec. R. S. VI. On a Substance from the Elm Tree, called Ulmin. By James XI. On a new Variety in the Breeds of Sheep. By Colonel David XII. Experiments to ascertain the coagulating Power of the Secretion of the gastric Glands. By Sir Everard Home, Bart. XV. A Method of drawing extremely fine Wires. By William Hyde Wollaston, M. D. Sec. R. S. XVI. Description of a single-lens Micrometer. By William Hyde Wollaston, M. D. Sec. R. S. XVII. Observation of the Winter Solstice of 1812, with the Mural Circle at Greenwich. By John Pond, Esq. Astronomer Royal, ERRATUM. Page 50, line 4, fur concave read convex. TRANSACTION S. I. On a new detonating Compound, in a Letter from Sir HUMPHRY DAVY, LL.D. F.R.S. to the Right Honourable Sir JOSEPH BANKS, Bart. K.B. P.R.S. Read November 5, 1812. MY DEAR SIR, I THINK it right to communicate to you, and through you to the Royal Society, such circumstances as have come to my knowledge respecting a new and a very extraordinary detonating compound. I am anxious that those circumstances should be made public as speedily as possible, because experiments upon the substance may be connected with very dangerous results; and because I have already mentioned the mode of preparing it to many of my chemical friends, to whom my experience may be useful in saving them from danger. About the end of September, I received a letter from a phi·losophical gentleman at Paris on some subjects of science, which contained the following paragraph: "Vous avez sans doute appris, Monsieur, la découverte qu'on a faite à Paris il y a près d'un an, d'une combinaison de gaz azote et de chlorine, qui a l'apparence d'une huile plus pesante que l'eau, et qui détonne avec toute la violence des métaux fulminans à la simple chaleur de la main, ce qui a privé d'un œil et d'un doigt l'auteur de cette découverte. Cette détonnation a lieu par la simple separation des deux gaz, comme celle de la combinaison d'oxigène et de chlorine; il y a également beaucoup de lumière et de la chaleur produites dans cette détonnation, où un liquide se decompose en deux gaz." The letter contained no account of the mode of preparation of this substance, nor any other details respecting it. So curious and important a result could not fail to interest me, particularly as I have long been engaged in experiments on the action of azote and chlorine, without gaining any decided proofs of their power of combining with each other. I perused with avidity the different French chemical and physical journals, especially Les Annales de Chimie, and Le Journal de Physique, of which the complete series of last year have arrived in this country, in hopes of discovering some detail respecting the preparation of this substance, but in vain. I was unable to find any thing relative to it in these publications, or in the Moniteur. It was evident from the notice, that it could not be formed in any operations in which heat is concerned; I therefore thought of attempting to combine azote and chlorine under circumstances which I had never tried before, that of presenting them to each other artificially cooled, the azote being in a nascent state. For this purpose I made a solution of ammonia, cooled it by a mixture of ice and muriate of lime, and slowly passed into it chlorine, cooled by the same means. There was immediately a violent action, accompanied by fumes of a pecu |