“I have had another severe attack of inflammation in the eye, and was obliged to have the conjunctiva and cornea punctured. I suspect the cause was some little imperceptible fragment. I am just recovering, and hope I shall see as well soon as with the other eye.” In the following April he was sufficiently recovered to resume the study of Dulong’s compound, and in a letter to Sir Joseph Banks, dated June 20th, 1813, and subsequently published in the _Philosophical Transactions_, he gives a number of details concerning its nature and composition. He accurately determined its specific gravity--viz. 1·653--but although he made a number of determinations of the amounts of its constituents by various methods, his deduction that it consisted of one proportion of nitrogen to four of chlorine was incorrect. The experiments of Gattermann, made with great skill and courage, have conclusively shown that the compound is, as long surmised, a trichloride of nitrogen. At about the same period, as we learn from a letter to his brother, dated April 4th, 1813, he attacked the chemistry of fluorine:-- “I am now quite recovered, and Jane [Lady Davy] is very well, and we have both enjoyed the last month in London. I have been hard at work. I have expelled fluorine from fluate of lead, fluate of silver, and fluate of soda by chlorine. It is a new acidifier, forming three powerful acids; hydrofluoric, silicated fluoric, and fluo-boric. It has the most intense energies of combination of any known body, instantly combining with all metals, and decomposing glass. Like the fabled waters of the Styx, it cannot be preserved, not even in the ape’s hoof. We have now a triad of supporters of combustion.” The results of Davy’s work were communicated to the Royal Society on July 8th, 1813. In his paper he states that M. Ampère of Paris had furnished him with many ingenious and original arguments in favour of the analogy between the muriatic and fluoric compounds, based partly upon his (Davy’s) views of the nature of chlorine, and partly upon reasonings drawn from the experiments of Gay Lussac and Thenard. After a short account of the main properties of the silicated fluoric acid gas (silicon fluoride), discovered by Scheele, fluoric acid (hydrofluoric acid), discovered by Scheele but first obtained pure by Gay Lussac and Thenard, and fluoric acid (boron fluoride), discovered by Gay Lussac and Thenard, he states that, on the hypothesis of M. Ampère-- “the silicated fluoric acid is conceived to consist of a peculiar undecompounded principle, analogous to chlorine and oxygen, united to the basis of silica, or _silicum_; the fluo-boric acid of the same principle united to boron; and the pure liquid fluoric acid as this principle united to hydrogen,”