Davy is here on the horns of a dilemma, but he ignores the difficulty, and, with characteristic “flexibility of adaptation,” proceeds to offer synthetical proofs “that the presence of light is absolutely essential to the production of phosoxygen.” The character of the “proofs” is sufficiently indicated by the following extracts:-- “When pure oxyd of lead is heated as much as possible, included from light, it remains unaltered; but when exposed to the light of a burning-glass, or even of a candle, phosoxygen is generated and the metal revivified.” “Oxygenated muriatic acid [chlorine] is a compound of muriatic acid, oxygen and light, as will be hereafter proved. The combined light is not sufficient to attract the oxygen from the base [muriatic acid] to form phosoxygen; but its attraction for oxygen renders the [oxygenated muriatic] acid decomposable. If this acid be heated in a close vessel and light excluded no phosoxygen is formed; but if it be exposed to the solar light, phosoxygen is formed; the acid loses its oxygen and light and becomes muriatic acid.” “A plant of Arenaria Tenuifolia planted in a pot filled with very dry earth, was inserted in carbonic acid, under mercury. The apparatus was exposed to the solar light, for four days successively, in the month of July. By this time the mercury had ascended considerably. The gas in the vessel was now measured. There was a deficiency of one-sixth of the whole quantity. After the carbonic acid was taken up by potash, the remaining quantity, equal to one-seventh of the whole, was _phosoxygen almost pure_. From this experiment, it is evident that carbonic acid is decomposed by two attractions; that of the vegetable for carbon and of light for oxygen: the carbon combines with the plant, and the light and oxygen combined are liberated in the form of phosoxygen.”