The effects produced by a second trial of its powers, were more extensive, and concentrated on the brain. In this instance, nearly six quarts undiluted, were accurately and fully inhaled. As on the former occasion, it immediately proved agreeably respirable, but before the whole quantity was quite exhausted, its agency was exerted so strongly on the brain, as progressively to suspend the senses of seeing, hearing, feeling, and ultimately the power of volition itself. At this period, the pulse was much augmented both in force and frequency; slight convulsive twitches of the muscles of the arms were also induced; no painful sensation, nausea, or languor, however, either preceded, accompanied, or followed this state, nor did a minute elapse before the brain rallied, and resumed its wonted faculties, when a sense of glowing warmth extending over the system, was speedily succeeded by a re-instatement of the equilibrium of health. The more permanent effects were (as in the first experiment) an invigorated feel of vital power, improved spirits, transient irritations in different parts, but not so characteristically rheumatic as in the former instance. Among the circumstances most worthy of regard in considering the properties and administration of this powerful aërial agent, may be ranked, the fact of its being (contrary to the prevailing opinion[223]) both highly respirable, and salutary, that it impresses the brain and system at large with a more or less strong and durable degree of pleasurable sensation, that unlike the effect of other violently exciting agents, no sensible exhaustion or diminution of vital power accrues from the exertions of its stimulant property, that its most excessive operation even, is neither permanently nor transiently debilitating; and finally, that it fairly promises under judicious application, to prove an extremely efficient remedy, as well in the vast tribe of diseases originating from deficient irritability and sensibility, as in those proceeding from morbid associations, and modifications, of those vital principles. If you should deem any thing contained in this cursory narrative capable of subserving in any degree the practical advantages likely to result from your scientific and valuable investigation of the genuine properties of the nitrous oxide, it is perfectly at your disposal. I am Your sincere friend, ROBERT KINGLAKE. _Bristol, June 14th, 1799._ To MR. DAVY.