The nature of the sensations themselves, which bore greater resemblance to a half delirious dream than to any distinct state of mind capable of being accurately remembered, contributes very much to increase the difficulty. And as it is above two months since I made the experiment, many of the minuter circumstances have probably escaped me.
I remain,
Yours, &c.
P. Roget.
To Mr. Davy.
VI. Letter from Mr. James Thomson.
The first time I respired nitrous oxide, the experiment was made under a strong impression of fear, and the quantity I breathed not sufficient, as you informed me, to produce the usual effect. I did not note very accurately my sensations. I remember I experienced a slight degree of vertigo after the third or fourth inspiration; and breathed with increased vigor, my inspirations being much deeper and more vehement than ordinary. I was enabled the next time I made the experiment, to attend more accurately to my sensations, and you have the observations I made on them at the time.
After the fourth inspiration, I experienced the same increased action of the lungs, as in the former case. My inspirations became uncommonly full and strong, attended with a thrilling sensation about the chest, highly pleasurable, which increased to such a degree as to induce a fit of involuntary laughter, which I in vain endeavoured to repress. I felt a slight giddiness which lasted for a few moments only. My inspirations now became more vehement and frequent; and I inhaled the air with an avidity strongly indicative of the pleasure I received. That peculiar thrill which I had at first experienced at the chest, now pervaded my whole frame; and during the two or three last inspirations, was attended with a remarkable tingling in my fingers and toes. My feelings at this moment are not to be described: I felt a high, an extraordinary degree of pleasure, different from that produced by wine, being divested of all its gross accompaniments, and yet approaching nearer to it than to any other sensation I am acquainted with.
I am certain that my muscular strength was for a time much increased. My disposition to exert it was such as I could not repress, and the satisfaction I felt in any violent exertion of my legs and arms is hardly to be conceived. These vivid sensations were not of long duration; they diminished insensibly, and in little more than a quarter of an hour I could perceive no difference between the state I was then in, and that previous to the respiration of the air.
The observations I made on repeating the experiment, do not differ from the preceding, except in the circumstance of the involuntary laughter, which I never afterwards experienced, though I breathed the air several times; and in the following curious fact, which, as it was dependent on circumstances, did not always occur.
Having respired the same quantity of air as usual, and with precisely the same effects, I was surprised to find myself affected a few minutes afterwards with the recurrence of a pain in my back and knees, which I had experienced the preceding day from fatigue in walking. I was rather inclined to deem this an accidental coincidence than an effect of the air; but the same thing constantly occurring whenever I breathed the air, shortly after suffering pain either from fatigue, or any other accidental cause, left no doubt on my mind as to the accuracy of the observation.
I have now given you the substance of the notes I made whilst the impressions were strong on my mind. I cannot add any thing from recollection that will at all add to the accuracy of this account, or assist those who have not respired this air, in forming a clearer idea of its extraordinary effects. It is extremely difficult to convey to others by means of words, any idea of particular sensations, of which they have had no experience. It can only be done by making use of such terms as are expressive of sensations that resemble them, and in these our vocabulary is very defective. To be able at all to comprehend the effects of nitrous oxide, it is necessary to respire it, and after that, we must either invent new terms to express these new and particular sensations, or attach new ideas to old ones, before we can communicate intelligibly with each other on the operation of this extraordinary gas.