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London, July 28, 1768.


GREATLY approve the epithet which you give, in your letter of the 8th of June, to the new method of treating the finall-pox, which you call the tonic or bracing method; I will take occasion, from it, to mention a practice to which I have accuttomed 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 inore agreeable to my constitution to bathe in another ele. ment, I mean cold air. With this view

I rise

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 least 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 consequences whatever result. ing from it, and that at least it does not injure my health, if it does not in fact contribute much to its preservation.I shall therefore call it for the future a bracing or tonic bath.

March 10, 1773. I shall not attempt to

n why damp clothes occasion colds, rather than wet ones, because I doubt the fact ; I imagine that neither the one nor the · VOL. I.


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 disposal. - 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 obstructing 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 another warmly clothed. He pursued the experiment in this alternate manner for eight hours successively, and found his perspiration almost double during those hours in which he was naked.




To the fame.

YOUR observations on the causes 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 sand 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 support of this opinion, are too numerous


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and too circunstantial not to deserve a certain degree of credit. As we are accustomed to see 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 necessity of nourishment, which animals experience in their ordinary state, proceeds from the continual waste of their substance by perfpiration; it will appear less incredible, that some animals in a torpid state, pero spiring less because they use no exercise, should have less need of aliment; and that others, which are covered with scales or shells, which stop perfpiration, such as land and sea turtles, serpents, and some species of fish, should be able to fubfist a considerable time without any nourishment whatever.- A plant, with its flowers, fades and dies immediately, if exposed to the air without having its roots immersed in a humid soil, from

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