It occurred to Mr. Jackson, a chemist of the United States, that it might be possible harmlessly to stupefy a patient through the inhalation of the vapour of sulphuric ether, to such an extent that a surgical operation would be unfelt by him. He communicated the idea to Mr. Morton, a dentist, who carried it into execution with the happiest results. The patient became insensible; a tooth was extracted; no pain seemed felt at the time, or was remembered afterwards, and no ill consequences followed. Led by the report of this success, in the course of the autumn of 1846, Messrs. Bigelow, Warren, and Heywood, ventured to employ the same means in surgical operations of a more serious description. The results obtained on these occasions were not less satisfactory than the first had been. Since then, in England, France, and Germany, the same interesting experiment has been repeated many hundred times, and the adoption of this, or of a parallel method, has become general in surgery. I withdraw from the present Letter a sketch which I had made from the “report” of Dr. Heyfelder, of the phenomena of etherization; for a year had barely elapsed, when the narcotizing agent recommended by Mr. Jackson was superseded by another, suggested and brought into use by Professor Simpson of Edinburgh. The inhalation of chloroform is found to be more rapid, uniform, and certain in its effects, and compassable in a simpler manner, than the inhalation of ether. Its brief phenomena are wound up by the production of stupor; they are remotely comparable to those produced by alcohol. Alas! the time is passed when I enjoyed the means of looking through, and forming a practical judgment upon discoveries like the present. Not the less, however, do I hail the advent of this as a boon to the art of surgery. The conception was original, bold and reasonable; its execution neat and scientific; its success wonderful. It established in the year 1847, to the satisfaction of the public and of the medical profession, that the exclusion of pain from surgical operations is a practicable idea, and the attempt to realize it a legitimate pursuit. Then, what is Mesmerism? The object of the inventor of the art was to cure diseases through the influence of a new force brought by him to bear upon the human frame.