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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 fmall pox, which you call the tonic or bracing method: I will take occafion, 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 fhock of the cold water has always appeared to me, generally speaking, as too violent, and I have found it much more agreeable to my conftitution to bathe in another element, I mean cold air. With this view I rife early almoft every morning, and fit in my chamber without any clothes whatever, half an hour or an hour, according to the feafon, 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 drefs myself, as fometimes happens, I make a supplement to my night's reft of one or two hours of the most pleasing fleep that can be imagined. I find no ill confequences whatever refulting from it, and that at leaft it does not injure my health, if it does not in fact contribute much to its prefervation.-I fhall therefore call it for the future a bracing or tonic bath.


March 10, 1793

I fhall not attempt to explain why damp clothes occafion colds, rather than wet ones, because I doubt the fact; I imagine that neither the one nor the other contribute to this effect, and that the caufes of colds are totally independent of wet and even of cold. I propose writing a fhort paper on this fubject, the firft moment of leifure I have at my difpofal.-In the mean time I can only say, that having fome 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 phyfician, who is making fome experiments with Sanctorius's balance, to eftimate the different proportions of his perspiration, when remaining one hour quite naked, and another warmly clothed. He purfued the experiment in this alternate manner for eight hours fucceflively, and found his perspiration almoft double during thofe hours in which he was naked.




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

A toad buried in fand will live, it is faid, until the fand becomes petrified; and then, being inclofed in the ftone, it may ftill live for we know not how many ages. The facts which are cited in fupport of this opinion, are too numerous and too circumftantial not to deferve 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 fupported in fuch a dungeon. But if we reflect, that the neceffity of nourishment, which animals experience in their ordinary ftate, proceeds from the continual wafte of their fubftance by perfpiration; it will appear lefs incredible, that fome animals in a torpid ftate, perfpiring lefs because they use no exercise, fhould have lefs need of aliment; and that others, which are covered with fcales or fhells, which stop perfpiration, fuch as land and fea turtles, ferpents, and fome fpecies of fifh, fhould be able to fubfift a confiderable time with


out any nourishment whatever.-A plant, with its flowers, fades and dies immediately, if expofed to the air without having its roots immerfed in a humid foil, from which it may draw a fufficient quantity of moisture, to fupply that which exhales from its fubftance, and is carried off continually by the air. Perhaps, however, if it were buried in quickfilver, it might preserve, for a confiderable space of time, its vegetable life, its fmell and colour. If this be the cafe, it might prove a commodious method of transporting from diftant countries thofe delicate plants which are unable to fuftain the inclemency of the weather at fea, and which require particular care and attention.

I have feen an inftance of common flies preferved in a manner fomewhat fimilar. They had been drowned in Madeira wine, apparently about the time when it was bottled in Virginia, to be fent 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 fun, I propofed making the experiment upon thefe. They were therefore expofed to the fun, upon a fieve which had been employed to ftrain them out of the wine. In lefs than three hours two of them began by degrees to recover life. They commenced by fome convulfive motions in the thighs, and at length they raised themfelves upon their legs, wiped their eyes with their fore feet, beat and brufhed their wings with their hind feet, and foon after began to fly, finding themselves in Old England, without knowing how they came thither. The third continued lifelefs until fun-fet, when, lofing all hopes of him, he was thrown away.

I wish it were poffible, from this inftance, to invent a method of embalming drowned perfons, in fuch a manner that they might be recalled to life at any period, however diftant; for having a very ardent defire to fee and obferve the ftate of America an hundred years hence, I fhould prefer, to an ordinary death, the being immersed in a cask of Madeira wine, with a few friends, until that time, then to be recalled to life by the folar warmth of my dear country! But fince, in all probability, we live in an age too early, and too near the infancy of science, to fee fuch an art brought in our time to its perfection, I muft, for the prefent, content myself with the treat, which you are fo kind as to promife me, of the refurrection of a fowl or a turkey-cock.


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