After having breathed five quarts of gas, I experienced for a short time a quickness and difficulty of breathing, which was succeeded by extreme languor, resembling fainting, without the very unpleasant sensation with which it is usually attended. It entirely deprived me of the power of speaking, but not of recollection, for I heard every thing that was said in the room during the time; and Mr. Davy’s remark “that my pulse was very quick and full.“ When the languor began to subside, it was succeeded by restlessness, accompanied by involuntary muscular motions. I was warmer than usual, and very sleepy for several hours. XVIII. _Letter from_ MR. M. M. COATES. I will, as you request, endeavour to describe to you the effect produced on me last Sunday fe’nnight by the nitrous oxide, and will at the same time tell you what was the previous state of my mind on the subject. When I sat down to breathe the gas, I believed that it owed much of its effect to the predisposing agency of the imagination, and had no expectation of its sensible influence on myself. Having ignorantly breathed a bag of common air without any effect, my doubts then arose to positive unbelief. After a few inspirations of the nitrous oxide, I felt a fulness in my head, which increased with each inhalation, until, experiencing symptoms which I thought indicated approaching fainting, I ceased to breathe it, and was then confirmed in my belief of its inability to produce in me any pleasurable sensation. But after a few seconds, I felt an immoderate flow of spirits, and an irresistible propensity to violent laughter and dancing, which, being fully conscious of the violence of my feelings, and of their irrational exhibition, I made great but ineffectual efforts to restrain; this was my state for several minutes. During the rest of the day, I experienced a degree of hilarity altogether new to me. For six or seven days afterwards, I seemed to feel most exquisitely at every nerve, and was much indisposed to my sedentary pursuits; this acute sensibility has been gradually diminishing; but I still feel somewhat of the effects of this novel agent. Your’s truly, M. M. COATES. To Mr. DAVY. _June 11th, 1800._ DIVISION III. _ABSTRACTS from ADDITIONAL DETAILS.—OBSERVATIONS on the EFFECTS of NITROUS OXIDE, by Dr. BEDDOES.—CONCLUSION._ I. _Abstracts from additional Details._ The trials related in the following abstracts, have been chiefly made since the publication of Dr. Beddoes’s Notice. Many of the individuals breathed the gas from pure curiosity. Others with a disbelief of its powers. * * * * *