This, indeed, is hardly agreeable to the hypothesis of most chemists, who suppose that the nitrous acid is stronger than the marine, so as to be capable of dislodging it from any base with which it may be combined; but it agrees with my own experiments on marine acid air, which shew that, in many cases, this _weaker acid_, as it is called, is capable of separating both the vitriolic and the nitrous acids from the phlogiston with which they are combined. On the other hand, the solution of metals in the different acids seems to shew, that the nitrous acid forms a closer union with phlogiston than the other two; because the air which is formed by the nitrous acid is not inflammable, like that which is produced by the oil of vitriol, or the spirit of salt. Also, the same weight of iron does not yield half the quantity of nitrous air that it does of inflammable. The great diminution of nitrous air by phlogiston is not easily accounted for, unless we suppose that its superabundant acid, uniting more intimately with the phlogiston, constitutes a species of _sulphur_ that is not easily perceived or catched; though, in the process with iron, and also in that with liver of sulphur, part of the redundant phlogiston forms such an union with the acid as gives it a kind of inflammability. It appears to me to be very probable, that the spirit of nitre might be exhibited in the form of _air_, if it were possible to find any fluid by which it could be confined; but it unites with quicksilver as well as with water, so that when, by boiling the spirit of nitre, the fumes are driven through the glass tube, fig. 8, they instantly seize upon the quicksilver through which they are to be conveyed, and uniting with it, form a substance that stops up the tube: a circumstance which has more than once exposed me to very disagreeable accidents, in consequence of the bursting of the phials. I do not know any inquiry more promising than the investigation of the properties of _nitre_, the _nitrous acid_, and _nitrous air_. Some of the most wonderful phenomena in nature are connected with them, and the subject seems to be fully within our reach. Sec. 2. _Speculations arising from the consideration of the similarity of the ELECTRIC MATTER and PHLOGISTON._