or from both indifferently; as, by the figure in the margin, whether the vessel a b is an artery or a vein, if the stream

it moves from b to a. Yet I cannot say I am certain the mere direction of the vessel will have no effect; I only suspect it, and am making a little machine to try an experiment with for satisfaction.

It is a siphon made of two large joints of Carolina cane

united at e, into which two small glass tubes, f and g, are to be inserted, one on the descending, and the other on the ascending side. I propose to fill the

siphon and the two glass tubes with water, and, when it is playing, unstop at the same instant the tops of both glass tubes, observing in which the water sinks fastest. You shall know the success. I conceive the pressure of the atmosphere on the apertures of the two glass tubes to be no way different from the pressure of the same on the mouths of the perspirants and absorbents, and if the water sinks equally in the two tubes, notwithstanding the direction of one against and the other with the stream, I shall be ready to think we must look out for another solution. You will say, perhaps, that it will then be time enough when the experiment is tried, and succeeds as I suspect; yet I cannot forbear attempting at one beforehand, while some thoughts are present in my mind.

If a new solution should be found necessary, this may be ready for consideration.

I do not remember, that any anatomist, that has fallen in my way, has assigned any other cause of the motion of the blood through its whole circle, than the contractile force of the heart, by which that fluid is driven with violence into the arteries, and so continually propelled by repetitions of the same force, till it arrives at the heart again. May we for our present purpose suppose another cause producing half the effect, and say that the ventricles of the heart, like syringes, draw when they dilate, as well as force when they contract? That this is not unlikely, may be judged from the valves nature has placed in the arteries, to prevent the drawing back of the blood in those vessels when the heart dilates, while no such obstacles prevent its sucking (to use the vulgar expression) from the veins. If this be allowed, and the insertion of the absorbents into the veins and of the perspirants into the arteries be agreed to, it will be of no importance in what direction they are inserted. For, as the branches of the arteries are continually lessening in their diameters, and the motion of the blood decreasing by means of the increased resistance, there must, as more is constantly pressed on behind, arise a kind of crowding in the extremities of those vessels, which will naturally force out what is contained in the perspirants that communicate with them. This lessens the quantity of blood, so that the heart cannot receive again by the veins all it had discharged into the arteries, which occasions it to draw strongly upon the absorbents, that communicate with them. And thus the body is continually perspiring and imbibing. Hence after long fasting the body is more liable to receive infection from bad air, and food,

before it is sufficiently chylified, is drawn crude into the blood by the absorbents that open into the bowels.

To confirm this position, that the heart draws, as well as drives the blood, let me add this particular. If you sit or lean long, in such a manner as to compress the principal artery that supplies a limb with blood, so that it does not furnish a due quantity, you will be sensible of a pricking pain in the extremities like that of a thousand needles; and the veins, which used to raise your skin in ridges, will be (with the skin) sunk into channels; the blood being drawn out of them, and their sides pressed so closely together that it is with difficulty and slowly that the blood afterwards enters them, when the compressed artery is relieved. If the blood was not drawn by the heart, the compression of an artery would not empty a vein, and I conjecture that the pricking pain is occasioned by the sides of the small vessels being pressed together.

I am not without apprehension, that this hypothesis is either not new, or, if it is new, not good for any thing. It may, however, in this letter, with the enclosed paper on a kindred subject, serve to show the great confidence I place in your candor, since to you I so freely hazard myself (ultra crepidam) in meddling with matters directly pertaining to your profession, and entirely out of the way of my own. If you give yourself the trouble of reading them, it is all I can modestly expect. Your silence about them afterwards will be sufficient to convince me, that I am in the wrong, and that I ought to study the sciences I dabble in, before I presume to set pen to paper. I will endeavour, however, to make you some amends by procuring you from better judges some better remarks on the rest of your piece, and shall

observe your caution not to let them know from whom I had it.

The piece on Fluxions I purpose shortly to read again, and that on the several species of matter, when you shall have what little I shall be able to say about them.

The members of our Society here are very idle gentlemen. They will take no pains. I must, I believe, alter the scheme and proceed with the papers I have, and may receive, in the manner you advise in one of your former letters. The mention of your former letters puts me in mind how much I am in arrear with you. Like some honest insolvent debtors, I must resolve to pay ready money for what I have hereafter, and discharge the old debt by little and little as I am able. The impertinence of these mosquitos to me (now I am in the humour of writing) prevents a great deal of mine to you, so that, for once, they are of some use in the world. I am, Sir,

Your most humble servant,

B. FRANKLIN.

50. TO JAMES READ1

DEAR JEMMY;

SATURDAY MORNING, August 17, 1745.

I have been reading your letter over again, and, since you desire an answer, I sit down to write you one; yet, as I write in the market, it will, I believe, be but a short one, though I may be long about it. I approve of your method of writing one's mind, when one is too warm to speak it with temper; but, being quite cool myself in this affair, I might as well speak as write, if I had an opportunity.

Are you an attorney by profession, and do you know no better how to choose a proper court in which to bring your action? Would you submit to the decision of a husband, a cause between you and his wife? Don't you know that all wives are in the right? It may be you don't, for you are But see, on this head, the learned

yet but a young husband. Coke, that oracle of the law, in his chapter De Jur. Marit. Angl. I advise you not to bring it to trial; for, if you do, you will certainly be cast.

Frequent interruptions make it impossible for me to go through all your letter. I have only time to remind you of the saying of that excellent old philosopher, Socrates, that, in differences among friends, they that make the first concessions are the wisest; and to hint to you, that you are in danger of losing that honour in the present case, if you are not very speedy in your acknowledgments, which I persuade myself you will be, when you consider the sex of your adversary.

Your visits never had but one thing disagreeable in them, that is, they were always too short. I shall exceedingly regret the loss of them, unless you continue, as you have begun, to make it up to me by long letters.

I am, dear Jemmy, with sincere love to our dearest Suky, your very affectionate friend and cousin,

SIR,

B. FRANKLIN.

51. TO CADWALLADER COLDEN

PHILADELPHIA, November 28, 1745.

I shall be very willing and ready, when you think proper to publish your piece on gravitation,' to print it at my own 1 "Cause of Gravitation," New York, 1745.- ED.