permit them to contract and dilate, and will show, in sensible degrees, by a movable hand upon a marked scale, the otherwise less sensible quantities of such contraction and dilatation. If these instruments are all kept in the same place while making, and are graduated together while subject to the same degrees of moisture or dryness, I apprehend you will have so many comparable hygrometers, which, being sent into different countries, and continued there for some time, will find and show there the mean of the different dryness and moisture of the air of those countries, and that with much less trouble than by any hygrometer hitherto in use.* With great esteem, I am, dear Sir, Your most obedient and most humble servant, B. FRANKLIN.

TO THE MARQUIS TURGOT.†

On a new-invented Stove.

Passy, 1 May, 1781.

SIR, I did intend, when in London, to have published a pamphlet, describing the new stove you mention, and for that purpose had a plate engraved, of which I send you an impression. But I have since been too much engaged in affairs to execute that intention. Its principle is that of a siphon reversed, operating on air in a manner somewhat similar to the operation of the common siphon on water. The funnel of the chimney is the longer leg, the vase is the shorter; and as, in the common siphon, the weight of water in the longer

* For the description of a hygrometer constructed by Mr. Nairne, in conformity with these directions, see his letter under the date of December 2d, 1783.- EDITOR.

Brother to the celebrated French financier and philosopher of the samne naine. - EDITOR.

leg is greater than that in the shorter leg; and thus in descending permits the water in the shorter leg to rise, by the pressure of the atmosphere; so in this aërial siphon, the levity of the air in the longer leg being greater than that in the shorter, it rises and permits the pressure of the atmosphere to force that in the shorter to descend. This causes the smoke to descend also, and in passing through burning coals it is kindled into flame, thereby heating more the passages in the iron box whereon the vase which contains the coals is placed; and retarding at the same time the consumption of the coals.

On the left hand of the engraving you see the machine put together and placed in a niche built for it in a common chimney. On the right hand the parts (except the vase) are shown separately. If you should desire a more particular explanation, I will give it to you viva voce, whenever you please. I think with you, that it is capable of being used to advantage in our kitchens, if one could overcome the repugnance of cooks to the using of new instruments and new methods. With great respect,

B. FRANKLIN.

TO FELIX VICQ D'AZYR.†

On the Long Retention of Infection in Dead Bodies

SIR,

after Sepulture.

Passy, 20 July, 1781.

I received the letter you some time since did me the honor of writing to me, accompanied with a

Probably referring to Plate XV. in the present volume. — EDITOR.

† Vicq d'Azyr was the physician to the Queen of France, and celebrated for his skill in medicine and his knowledge of science. His works were published in six volumes. - EDITOR.

VOL. VI.

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number of the pieces, that were distributed at the last public meeting of the Royal Society of Medicine. I shall take care to forward them to different parts of America, as desired. Be pleased to present my thanks to the Society for the copy sent me of the curious and useful reports relating to the sepulture in the island of Malta. I should be glad of another copy, if it can be spared, being desirous of sending one to each of the philosophical societies in America.

With respect to the length of time during which the power of infection may be contained in dead bodies, which is considered in that report, I would mention to you three facts, which, though not all of equal importance or weight, yet methinks it may be well to preserve a memorandum of them, that such observations may be made when occasion offers, as are proper to confirm or invalidate them.

While I resided in England, I read in a newspaper, that in a country village at the funeral of a woman whose husband had died of the smallpox thirty years before, and whose grave was dug so as to place her by his side, the neighbours attending the funeral were offended with the smell arising out of the grave, occasioned by a breach in the husband's old coffin, and twenty-five of them were in a few days taken ill with that distemper, which before was not in that village or its neighbourhood, nor had been for the number of years above mentioned.

About the years 1763 or 1764, several physicians of London, who had been present from curiosity at the dissection of an Egyptian mummy, were soon after taken ill of a malignant fever, of which they died. Opinions were divided on this question. It was thought by some that the fever was caused by infection from the mummy; in which case the disease it

died of must have been embalmed as well as the body. Others who considered the length of time; at least two thousand years, since that body died, and also that the embalming must be rather supposed to destroy the power of infection, imagined the illness of these gentlemen must have had another original.

About the year 1773, the captain of a ship, which had been at the island of Teneriffe, brought from thence the dried body of one of the ancient inhabitants of that island, which must have been at least three hundred years old, that custom of drying the dead. there having been so long discontinued. Two members of the Royal Society went to see that body. They were half an hour in a small close room with it, examining it very particularly. The next day they were both affected with a singularly violent cold,* attended with uncommon circumstances, which continued a long time. On comparing together the particulars of their disorder, they agreed in suspecting that possibly some effluvia from the body might have been the occasion of that disorder in them both; perhaps they were mistaken. But, as we do not yet know with certainty how long the power of infection may in some bodies be retained, it seems well in such cases to be cautious till farther light shall be obtained.

I wish it were in my power to contribute more essentially in advancing the good work the Society are so laudably engaged in. Perhaps some useful hints may be extracted from the enclosed paper of Mr. Small's. It is submitted to your judgment; and, if you should find any thing in it worthy of being communicated to the Society, and of which extracts may

* Cold is a general name given by the English to all sorts of rheums and catarrhs.

† See the article on Ventilation, by Mr. Small, above, p. 307.

be useful if printed in the Memoirs, it will be a pleasure to me; who am, with great esteem and respect, Sir, &c.

B. FRANKLIN.

P. S. July 24. Since writing the above, I have met with the following article in the Courier de l'Europe of the 13th instant, viz.

Extrait d'une Lettre d'Edimbourg, en date du 30 Juin.

"J'apprends par une personne qui vient de Montrose, que la fièvre épidémique qui s'est manifestée il y a quelque tems dans le Méarns, désole encore aujourd'hui ce voisinage avec tant de violence qu'un de ses amis a été invité à assister à quinze enterrements dans un seul jour. On dit que cette maladie doit son origine à la folle curiosité de quelques paysans, qui, à la Chandeleur dernière, exhumèrent quelques personnes mortes de la peste dans le siècle précédent, et qu'on avoit enterrées dans le Moss de Arnhall. Ce qui est arrivé à la famille de M. Robert Aikenhead est singulièrement malheureux; vers le milieu du mois dernier il a été attaqué de cette contagion, et elle s'est communiquée au reste de sa famille, consistant en neuf personnes, dont deux sont mortes ainsi que lui, et le reste n'est pas sans danger."

Translation.

Extract of a Letter from Edinburgh, dated June 30th.

"I understand by a person just returned from Montrose, that the epidemic fever which has made its appearance in the county of Mearns, ravages that neighbourhood with such violence, that one of his friends was invited to attend fifteen funerals on the same day.