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LIII: A CONJECTURE AS TO THE CAUSE OF THE HEAT OF THE BLOOD IN HEALTH, AND OF THE COLD AND HOT FITS OF SOME FEVERS 1 - Benjamin Franklin, The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753 [1904]

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The Works of Benjamin Franklin, including the Private as well as the Official and Scientific Correspondence, together with the Unmutilated and Correct Version of the Autobiography, compiled and edited by John Bigelow (New York: G.P. Putnam’s Sons, 1904). The Federal Edition in 12 volumes. Vol. II (Letters and Misc. Writings 1735-1753).

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LIII

A CONJECTURE AS TO THE CAUSE OF THE HEAT OF THE BLOOD IN HEALTH, AND OF THE COLD AND HOT FITS OF SOME FEVERS1

The parts of fluids are so smooth, and roll among one another with so little friction, that they will not by any (mechanical) agitation grow warmer. A phial half full of water shook with violence and long continued, the water neither heats itself nor warms the phial. Therefore the blood does not acquire its heat either from the motion and friction of its own parts, or its friction against the sides of its vessels.

But the parts of solids, by reason of their closer adhesion, cannot move among themselves without friction, and that produces heat. Thus, bend a plummet to and fro, and, in the place of bending, it shall soon grow hot. Friction on any part of our flesh heats it. Clapping of the hands warms them. Exercise warms the whole body.

The heart is a thick muscle, continually contracting and dilating nearly eighty times in a minute. By this motion there must be a constant interfrication of its constituent solid parts. That friction must produce a heat, and that heat must consequently be continually communicated to the perfluent blood.

To this may be added, that every propulsion of the blood by the contraction of the heart distends the arteries, which contract again in the intermission; and this distension and contraction of the arteries may occasion heat in them, which they must likewise communicate to the blood that flows through them.

That these causes of the heat of the blood are sufficient to produce the effect, may appear probable, if we consider that a fluid once warm requires no more heat to be applied to it in any part of time to keep it warm, than what it shall lose in an equal part of time. A smaller force will keep a pendulum going, than what first set it in motion.

The blood, thus warmed in the heart, carries warmth with it to the very extremities of the body, and communicates to them; but, as by this means its heat is gradually diminished, it is returned again to the heart by the veins for a fresh calefaction.

The blood communicates its heat, not only to the solids of our body, but to our clothes, and to a portion of the circumambient air. Every breath, though drawn in cold, is expired warm; and every particle of the materia perspirabilis carries off with it a portion of heat.

While the blood retains a due fluidity, it passes freely through the minutest vessels, and communicates a proper warmth to the extremities of the body. But when by any means it becomes so viscid as not to be capable of passing those minute vessels, the extremities, as the blood can bring no more heat to them, grow cold.

The same viscidity in the blood and juices checks or stops the perspiration, by clogging the perspiratory duct, or, perhaps, by not admitting the perspirable parts to separate. Paper wet with size and water will not dry so soon as if wet with water only.

A vessel of hot water, if the vapor can freely pass from it, soon cools. If there be just fire enough under it to add continually the heat it loses, it retains the same degree. If the vessel be closed, so that the vapor may be retained, there will from the same fire be a continual accession of heat to the water, till it rises to a great degree. Or, if no fire be under it, it will retain the heat it first had for a long time. I have experienced, that a bottle of hot water stopped, and put in my bed at night, has retained so much heat seven or eight hours, that I could not in the morning bear my foot against it, without some of the bedclothes intervening.

During the cold fit, then, perspiration being stopped, great part of the heat of the blood, that used to be dissipated, is confined and retained in the body; the heart continues its motion, and creates a constant accession to that heat; the inward parts grow very hot, and, by contact with the extremities, communicate that heat to them. The glue of the blood is by this heat dissolved, and the blood afterwards flows freely, as before the disorder.

LIV

TO CADWALLADER COLDEN

Philadelphia, 27 January, 1748.

Dear Sir:—

I received your favor relating to the cannon. We have petitioned our Proprietors for some, and have besides wrote absolutely to London for a quantity, in case the application to the Proprietors should not succeed; so that, accidents excepted, we are sure of being supplied some time next summer. But, as we are extremely desirous of having some mounted early in the spring, and perhaps, if your engineer should propose to use all you have, the works he may intend will not very soon be ready to receive them, we should think ourselves exceedingly obliged to your government, if you would lend us a few for one year only. When you return to New York, I hope a great deal from your interest and influence.

Mr. Read, to whom Osborne consigned your books,1 did not open or offer them for sale till within these two weeks, being about to remove when he received them, and having till now no conveniency of shelves, &c. In our two last papers he has advertised generally, that he has a parcel of books to sell—Greek, Latin, French, and English,—but makes no particular mention of the Indian History; it is therefore no wonder that he has sold none of them, as he told me a few days since. I had one of them from London, which I sent you before any of my friends saw it. So, as no one here has read it but myself, I can only tell you my own opinion, that it is a well-written, entertaining, and instructive piece, and must be exceedingly useful to all those colonies which have any thing to do with Indian affairs.

You have reason to be pleased with the mathematician’s envious expression about your tract on gravitation. I long to see from Europe some of the deliberate and mature thoughts of their philosophers upon it.

To obtain some leisure I have taken a partner1 into the printing-house; but, though I am thereby a good deal disengaged from private business, I find myself still fully occupied. The association, lottery, and batteries fill up at present a great part of my time.2

I thank you for communicating the sheet on the first principles of morality, the continuation of which I shall be glad to see. I am, &c.,

B. Franklin.

[1 ]This piece I have found in Franklin’s handwriting among the papers of Cadwallader Colden. Its date is uncertain, but it was probably written before the year 1750.—Sparks.

[1 ]Mr. Colden’s History of the Five Indian Nations, which was published in London, and copies of which were sent over to be sold in Philadelphia.

[1 ]David Hall, a Scotchman by birth, and a friend of Mr. Strahan, who had worked in the same office with Franklin as a journeyman printer in London. His partnership with Franklin continued eighteen years, during which time he had the principal charge of the business. He conducted the Pennsylvania Gazette, and was likewise a bookseller and stationer. He died on the 17th of December, 1772, at the age of fifty-eight years. See Thomas’s History of Printing, vol. ii, p. 54.

[2 ]In his Autobiography Franklin says: “I proposed a Lottery to defray the expense of building a battery below the town, and furnishing it with cannon. It filled expeditiously, and the battery was soon erected.” “Mr. Logan put into my hands sixty pounds, to be laid out in lottery tickets for the battery, with directions to apply what prizes might be drawn wholly to that service.” The following memoranda, found in Franklin’s handwriting, show his manner of proceeding on this occasion:

“Proposed, That the Managers of the Lottery be applied to, to appoint suitable persons to go down the river to the Capes, and there consult with the persons in authority, and concert with them the modes of conveying intelligence to Philadelphia, whether by express or otherwise, when any enemies appear of such force as to make an alarm necessary, or even such as may endanger our trade; who may likewise, in returning, land at such places as they judge suitable to give signals from, and endeavour to agree with the neighbouring inhabitants to keep watch and give the signals that may be agreed on, and engage to furnish them with guns, tar-barrels, or whatever else may be necessary for that purpose.

That, for the more certain alarming the country on any occasion, as soon as the commander-in-chief at Philadelphia is well-informed of the approach, on our coasts, of any considerable force of the enemy, letters and orders may be despatched by expresses to the colonels of some or all of the regiments, as the occasion may require, who may immediately communicate the same to the other officers of the regiments, and they to the men of the respective companies, who are immediately to meet at their usual place of rendezvous, and from thence march to such place as the colonel shall appoint for assembling his regiment; and when all the companies are assembled, the regiment to march to such place as the commander-in-chief shall have directed.

That, in case of any attempt on the inhabitants of the frontiers by small parties, as the Indian custom is, the superior officers of the regiment, being well-informed of the facts, may despatch away on horseback suitable bodies of active men, well acquainted with the woods, to such places or passes among the mountains, or near the conflux of rivers, by which it is probable the enemy must endeavour to make their retreat, and there to take post and lie in wait till their return, keeping proper scouts or sentinels at a distance of the body to give notice of their approach; by which means they may be cut off, and the prisoners they take may be recovered; a few instances of which would probably much intimidate those cowardly people, and make them afraid of attempting to attack us hereafter. And that such places may be known to more people, it might be proper for the officers beforehand to make a few journeys to them, guided by Indian traders or hunters, accompanied by such of their men as would be suitable to act on occasion and are disposed that way, observing and pointing out all the proper places for ambushes, &c. The expense of which journeys might be defrayed by the managers of the lottery.

That, if there be certain accounts of any large body of the enemy marching towards any part of the frontiers, the colonels of the nearest frontier regiments may despatch expresses to the commander-in-chief at Philadelphia, with the vouchers of the intelligence, from whom orders may issue to raise such force as may be necessary to march to the assistance of such threatened frontier.

That the people on the frontiers be advised to pitch on some suitable places at proper distances, and there enclose pieces of ground with palisades or stockades, so as to make them defensible against Indians, whereto, on occasion, their wives, children, and ancient persons may retire in time of danger. In parts where there may not be had sufficient voluntary labor to erect such defences, and the neighbours, being poor, cannot bear the expense, some assistance might be obtained from the lottery managers, if another lottery should go on.

That those managers be applied to, to offer rewards by public declaration to such as should be maimed in action, and pensions to poor widows, whose husbands should happen to fall in defence of their country.

That a number of spades, pickaxes, shovels, &c., be provided for the city regiment, to be used by the negroes and others as pioneers for casting up sudden intrenchments on occasion.”—Editor.