The body of evidence by which Davy overthrew this doctrine, and established the undecompounded nature of oxymuriatic acid, is to be found in a succession of papers read before the Royal Society, _viz._ in that already announced,--in his Bakerian Lecture for 1810,--and in a subsequent memoir read in February 1811. It will be impossible for me to follow the author through all the intricacies of the enquiry; but I shall seize upon some of its more prominent points, and give a general outline of its bearings. No sooner had his suspicions been excited with regard to the compound nature of oxymuriatic acid, than it occurred to him that, if oxygen were really present in that body, he might readily obtain it from some of its compounds; that, for instance, its combination with tin would yield an oxide of that metal by ammonia; while those with phosphorus would furnish, on analysis, either the phosphor_ous_, or phosphor_ic_ acid. But after experiments in which the presence of water was most cautiously excluded, the results he had anticipated were not obtained. In the place of an oxide of tin, the product, on the application of heat, volatilized in dense and pungent fumes; and, instead of obtaining an acid of phosphorus, a body possessing new and unexpected properties resulted. Again,--it had been stated, in confirmation of the theory that recognised the presence of oxygen in oxymuriatic acid, that when this latter body and ammonia were made to act upon each other, water was formed: our chemist frequently repeated the experiment, and convinced himself that such was not the fact. It had been shown by Mr. Cruickshank, and more recently proved by MM. Gay Lussac and Thénard, that oxymuriatic acid and hydrogen, when mixed in nearly equal proportions, produce a matter almost entirely condensable by water, which is common muriatic acid; and that water is not deposited in the operation. Davy made many experiments on the subject, and he found, that when these gases were mingled together in equal volumes over water, introduced into an exhausted vessel, and fired by the electric spark, muriatic acid resulted, although, at the same time, there was a certain degree of condensation, and a slight deposition of vapour; but on repeating the experiment in a manner still more refined, and by carefully drying the gases, such condensation became proportionally less. When, in addition to the above experimental evidence, it is stated that MM. Gay Lussac and Thénard had proved, by a copious collection of instances, that in the usual cases where oxygen is eliminated from oxymuriatic acid, water is always present, and muriatic acid gas is formed; and as it has been moreover shown that oxymuriatic is converted into muriatic acid gas by combining with hydrogen, it is scarcely possible to avoid the conclusion, that the oxygen is derived from the decomposition of water, and not from that of the acid.