The operation being over, the strength and turbulence of my sensations subsided. To this succeeded a state of feeling uncommonly serene and tranquil. Every nerve being gently agitated with a lively enjoyment. It was natural to expect that the effect of this experiment, would eventually prove debilitating. So far from this I continued in a state of high excitement the remainder of the day after two o’clock, the time of the experiment, and experienced a flow of spirits not merely chearful, but unusually joyous. GEORGE BURNET. X. _Detail of_ MR. T. POPLE. A disagreeable sensation as if breaking out into a profuse perspiration, tension of the tympanum, cheeks and forehead; almost total loss of muscular power; afterwards increased powers both of body and mind, very vivid sensations and highly pleasurable. Those pleasant feelings were not new, they were felt, but in a less degree, on ascending some high mountains in Glamorganshire. On taking it the second time, there was a disagreeable feeling about the face. In a fewseconds, the feelings became pleasurable; all the faculties absorbed by the fine pleasing feelings of existence without consciousness; an involuntary burst of laughter. THOMAS POPLE. XI. _Detail of_ MR. HAMMICK. Having never heard any thing of the mode of operation of nitrous oxide, I breathed gas in a silk bag for some time, and found no effects, but oppression of respiration. Afterwards Mr. Davy told me that I had been breathing atmospheric air. In a second experiment made without knowing what gas was in the bag, I had not breathed half a minute, when from the extreme pleasure I felt, I unconciously removed the bag from my mouth; but when Mr. Davy offered to take it from me, I refused to let him have it, and said eagerly, “let me breathe it again, it is highly pleasant! it is the strongest stimulant I ever felt!“ I was cold when I began to respire, but had immediately a pleasant glow extending to my toes and fingers. I experienced from the air a pleasant taste which I can only call sweetly astringent; it continued for some time: the sense of exhilaration was lasting. This air Mr. Davy told me was nitrous oxide. In another experiment, when I breathed a small dose of nitrous oxide, the effects were slight, and sometime afterwards I felt an unusual yawning and languor. The last time that I breathed the gas, the feelings were the most pleasurable I ever experienced; my head appeared light, there was a great warmth in the back and a general unusual glow; the taste was distinguishable for some time as in the former experiment. My ideas were more vivid, and followed the natural order of association. I could not refrain from muscular action. STEPHEN HAMMICK, Junr. _Sept. 15th._ XII. _Detail of_ DR. BLAKE.