Laughing-gas, indeed threatened to become, like Priestley’s dephlogisticated air, “a fashionable article in luxury.” Monsieur Fiévée, in his “Lettres sur l’Angleterre, 1802,” names it in the catalogue of follies to which the English were addicted, and says the practice of breathing it amounted to a national vice! Davy had no sooner discovered that the gas might be respired, than he proceeded to attack the whole subject of the chemistry of the oxides of nitrogen, and of nitrous oxide in particular, and after ten months of incessant labour he put together the results of his observations in an octavo volume, entitled, “Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide, or Dephlogisticated Nitrous Air, and its Respiration. By Humphry Davy, Superintendent of the Medical Institution.” The book appeared in the summer of 1800, and immediately re-established its author’s character as an experimentalist. Thomson, in his “History of Chemistry,” says of it: “This work gave him at once a high reputation as a chemist, and was really a wonderful performance, when the circumstances under which it was produced are taken into consideration.” In spite, however, of the eulogies with which it was welcomed, its sale was never very extensive, and a second edition was not required. In fact, the work as a whole was hardly calculated to attract the general public, whose only concern with laughing-gas was in its powers as an exhilarant. Indeed, this aspect of the question is not wholly lost on Davy himself, who is careful to point out that “if the pleasurable effects or medical properties of the nitrous oxide should ever make it an article of general request, it may be procured with much less time, labour, and expense than most of the luxuries, or even necessaries, of life”; and in a footnote he adds. “A pound of nitrate of ammonia costs 5s. 10d. (its present price is 9d.!). This pound, properly decomposed, produces rather more than 34 moderate doses of the air, so that the expense of a dose is about 2d. What fluid stimulus can be procured at so cheap a rate?”