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when it appeared that, by following too quick, I lowered the kite too much; by doing which occasionally I made it rise again.-I have never fince that time practised this fingular mode of swimming, though I think it not impossible to cross in this manner from Dover to Calais. The ket-boat, however, is still preferable.

The pac,




London, July 28, 1768. I GREATLY approve the epithet which you give, in your letter of the 8th of June,' to the new method of treating the small.pox, which you call the tonic or bracing method : I will take occasion, from it, to mention a practice to which I have accustomed myself. You know the cold bath has long been in vogue here as a tonic; but the shock of the cold water has always appeared to me, generally speaking, as too violent, and I have found it much more agreeable to my constitution to bathe in another element, I mean cold air. With this view I rise early almost every morning, and fit in my chamber without any clothes whatever, half an hour or an hour, according to the season, either reading or writing. This practice is not in the lealt painful, but, on the contrary, agreeable; and if I return to bed afterwards, before I dress myself, as sometimes happens, I make a supplement to my night's rest of one or two hours of the most pleasing sleep that can be imagined. I find no ill conse- . quences whatever resulting from it, and that at least it does not injure my health, if it does not in fact contribute much to its preservation.-I Mall therefore call it for the future a bracing or tonic bath.


March 10, 1793I shall not attempt to explain why damp clothes occafion colds, rather than wet ones, be. cause I doubt the fact; I imagine that neither the one nor the other contribute to this effect, and that the causes of colds are totally independent of wet and even of cold. I propose writing a short paper on this subject, the first moment of leisure I have at my difpofal. In the mean time I can only say, that having some fufpicions that the common notion, which attributes to cold the property of stopping the pores and obftructing perfpiration, was ill founded, I engaged a young physician, who is making some experiments with Sanctorius's balance, to estimate the different proportions of his perspiration, when remaining one hour quite naked, and ano. ther warmly clothed. He pursued the experiment in this alternate manner for eight hours fucceflively, and found his perspiration almost double during those hours in which he was paked.




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Your obfervations on the caufes of death, and the experiments which you propose for recalling to life those who appear to be killed by lightning, demonstrate equally your fagacity and humanity. It appears that the doctrines of life and death, in general, are yet but little understood.

A toad buried in fand will live, it is said, until the fand becomes petrified; and then, being inclosed in the stone, it may still live for we know not how many ages. The facts which are cited in fupport of this opinion, are too numerous and too circumstantial not to deserve a certain degree of credit. As we are accustomed to fee all the animals with which we are acquainted eat and drink, it appears to us difficult to conceive how a toad can be supported in such a dungeon. But if we reflect, that the neceffity of nourishment, which animals experience in their ordinary state, proceeds from the continual waste of their fubstance by perspiration; it will appear less incredible, that some animals in a torpid state, perfpiring less because they use no exercise, should have lefs need of aliment; and that others, which are covered with scales or shells, which stop perspiration, fuch as land and fea turtles, serpents, and fome species of fish, should be able to fubfist a considerable time with


may draw

out any nourishment whatever.--A plant, with its flowers, fades and dies immediately, if exposed to the air without having its roots im. mersed in a humid foil, from which it a sufficient quantity of moisture, to supply that which exhales from its substance, and is carried off continually by the air. Perhaps, however, if it were buried in quicksilver, it might preserve, for a considerable space of time, its vegetable life, its smell and colour. If this be the case, it might prove a commodious method of transporting from diftant countries those delicate plants which are unable to sustain the inclemency of the weather at fea, and which require particular care and attention.

I have seen an instance of common flies preserved in a manner fomewhat similar. They had been drowned in Madeira wine, apparently about the time when it was bottled in Virginia, to be sent to London. At the opening of one of the bottles, at the house of a friend where I was, three drowned flies fell into the first glass which was filled. Having heard it remarked that drowned flies were capable of being revived by the rays of the sun, I proposed making the experiment upon these. They were therefore exposed to the sun, upon a sieve which had been employed to strain them out of the wine. In less than three hours two of them began by degrees to recover life. They commenced by some convulsive motions in the thighs, and at length they raised themselves upon their legs, wiped their eyes with their fore feet, beat and brushed their wings with their hind feet, and soon after began to fly, finding themselves in Old England, without knowing how they came thither. The third continued lifeless until sun-fet, when, losing all hopes of him, he was thrown away.

I wish

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