From a letter to Mr. Davies Gilbert, dated April 10th, 1799, we learn that he had now begun to investigate the effects of gases in respiration. In the early part of the year he had removed to a house in Dowry Square, Clifton, where he had fitted up a laboratory. After thanking his friend for his critical remarks on his recently published essays, he says: “Your excellent and truly philosophic observations will induce me to pay greater attention to all my positions.... I made a discovery yesterday which proves how necessary it is to repeat experiments. The gaseous oxide of azote is perfectly respirable when pure. It is never deleterious but when it contains nitrous gas. I have found a mode of obtaining it pure, and I breathed to-day, in the presence of Dr. Beddoes and some others, sixteen quarts of it for near seven minutes. It appears to support life longer than even oxygen gas, and absolutely intoxicated me. Pure oxygen gas produced no alteration in my pulse, nor any other material effect; whereas this gas raised my pulse upwards of twenty strokes, made me dance about the laboratory as a madman, and has kept my spirits in a glow ever since. Is not this a proof of the truth of my theory of respiration? for this gas contains more light in proportion to its oxygen than any other, and I hope will prove a most valuable medicine. “We have upwards of eighty out-patients in the Pneumatic Institution, and are going on wonderfully well.” This observation of the respirability of nitrous oxide, and of the effects of its inhalation, was quickly confirmed. Southey, Coleridge, Tobin (the dramatist), Joseph Priestley, the son of the chemist, the two Wedgwoods, and a dozen other people of lesser note were induced to breathe the gas and to record their sensations. The discovery was soon noised abroad; Dr. Beddoes dispatched a short note to Nicholson’s Journal, and the fame of the Pneumatic Institution went up by leaps and bounds. Maria Edgeworth, who was at the time on a visit to her sister, thus writes:-- “A young man, a Mr. Davy, at Dr. Beddoes’, who has applied himself much to chemistry, has made some discoveries of importance, and enthusiastically expects wonders will be performed by the use of certain gases, which inebriate in the most delightful manner, having the oblivious effects of Lethe, and at the same time giving the rapturous sensations of the Nectar of the Gods! Pleasure even to madness is the consequence of this draught. But faith, great faith, is I believe necessary to produce any effect upon the drinkers, and I have seen some of the adventurous philosophers who sought in vain for satisfaction in the bag of _Gaseous Oxyd_, and found nothing but a sick stomach and a giddy head.”