I was in England, I formed a portable copying press, on the principles of the large one they make here, for copying letters. I had a model made there, and it has answered perfectly. A workman here has made several from that model. The itinerent temper of your court will, I think, render one of these useful to you. You must, therefore, do me the favor to accept of one. I have it now in readiness, and shall send it by the way of Bayonne, to the care of Mr. Alexander there, unless Don Miguel de Lardizabal can carry it with him.
My hand admonishes me it is time to stop, and that I must defer writing to Mr. Barclay till to-morrow.
I have the honor to be, with sentiments of the highest esteem and respect, dear Sir, your most obedient, and most humble servant.
TO MR. VAUGHAN
Sir,—When I had the honor of seeing you in London, you were so kind as to permit me to trouble you sometimes with my letters, and particularly on the subject of mathematical or philosophical instruments. Such a correspondence will be too agreeable to me, and at the same time, too useful, not to avail myself of your permission. It has been an opinion pretty generally received among philosophers, that the atmosphere of America is more humid than that of Europe. Monsieur de Buffon makes this hypothesis one of the two pillars whereon he builds his system of the degeneracy of animals in America. Having had occasion to controvert this opinion of his, as to the degeneracy of animals there, I expressed a doubt of the fact assumed, that our climates are more moist. I did not know of any experiments which might authorize a denial of it. Speaking afterwards on the subject with Dr. Franklin, he mentioned to me the observations he had made on a case of magnets, made for him by Mr. Nairne in London. Of these you will see a detail, in the second volume of the American Philosophical Transactions, in a letter from Dr. Franklin to Mr. Nairne, wherein he recommends to him to take up the principle therein explained, and endeavor to make an hygrometer, which, taking slowly the temperature of the atmosphere, shall give its mean degree of moisture, and enable us thus to make with more certainty, a comparison between the humidities of different climates. May I presume to trouble you with an inquiry of Mr. Nairne, whether he has executed the Doctor's idea? and if he has, to get him to make for me a couple of the instruments he may have contrived. They should be made of the same piece, and under like circumstances, that sending one to America, I may rely on its indications there, compared with those of the one I shall retain here. Being in want of a set of magnets also, I would be glad if he would at the same time send me a set, the case of which should be made as Dr. Franklin describes his to have been, so that I may repeat his experiment. Colonel Smith will do me the favor to receive these things from Mr. Nairne, and to pay him for them.
I think Mr. Rittenhouse never published an invention of his in this way, which was a very good one. It was of an hygrometer which, like the common ones, was to give the actual moisture of the air. He has two slips of mahogany about five inches long, three-fourths of an inch broad, and one-tenth of an inch thick, the one having the grain running lengthwise, and the other crosswise. These are glued together by their faces, so as to form a piece five inches long, three-fourths of an inch broad, and one third of an inch thick, which is stuck by its lower end into a little plinth of wood, presenting their edge to the view. The fibres of the wood you know are dilated, but not lengthened by moisture. The slip, therefore, whose grain is lengthwise, becomes a standard, retaining always the same precise length. That which has its grain crosswise, dilates with moisture, and contracts for the want of it. If the right hand piece be the cross grained one, when the air is very moist, it lengthens, and forces its companion to form a kind of interior annulus of a circle on the left. When the air is dry, it contracts, draws its companion to the right, and becomes itself the interior annulus. In order to show this dilatation and contraction, an index is fixed on the upper end of two of the slips; a plate of metal or wood is fastened to the front of the plinth, so as to cover the two slips from the eye. A slit, being nearly the portion of a circle, is cut in this plate, so that the shank of the index may play freely through its whole range. On the edge of the slit is a graduation. The objection to this instrument is, that it is not fit for comparative observations, because no two pieces of wood being of the same texture exactly, no two will yield exactly alike to the same agent. However, it is less objectionable on this account, than most of the substances used. Mr. Rittenhouse had a thought of trying ivory; but I do not know whether he executed it. All these substances not only vary from one another at the same time, but from themselves at different times. All of them, however, have some peculiar advantages, and I think this, on the whole, appeared preferable to any other I had ever seen. Not knowing whether you had heard of this instrument, and supposing it would amuse you, I have taken the liberty of detailing it to you.
I beg you to be assured of the sentiments of perfect esteem and respect with which I have the honor to be, Sir, your most obedient, and most humble servant.
TO JOHN JAY
Sir,—I had the honor of addressing you on the 12th of the last month; since which, your favor of October the 12th has been received, enclosing a copy of the resolution of Congress for recalling Mr. Lambe. My letter by Mr. Randall informed you that we had put an end to his powers, and required him to repair to Congress. I lately received a letter from him, dated Alicant, October the 10th, of which I have the honor to enclose you a copy; by which, you will perceive that the circumstance of ill health, either true or false, is urged for his not obeying our call. I shall immediately forward the order of Congress. I am not without fear, that some misapplication of the public money may enter into the causes of his declining to return. The moment that I saw a symptom of this in his conduct, as it was a circumstance which did not admit the delay of consulting Mr. Adams, I wrote to Mr. Carmichael, to stop any moneys which he might have in the hands of his banker. I am still unable to judge whether he is guilty of this or not, as by the arrangements with Mr. Adams, who alone had done business with the bankers of the United States, in Holland, Mr. Lambe's drafts were to be made on him, and I know not what their amount has been. His drafts could not have been negotiated, if made on us both, at places so distant. Perhaps it may be thought, that the appointment of Mr. Lambe was censurable in the moment in which it was made. It is a piece of justice, therefore, which I owe to Mr. Adams, to declare that the proposition went first from me to him. I take the liberty of enclosing you a copy of my letter to Mr. Adams, of September the 24th, 1785, in which that proposition was made. It expresses the motives operating on my mind in that moment, as well as the cautions I thought it necessary to take. To these must be added, the difficulty of finding an American in Europe fit for the business, and willing to undertake it. I knew afterwards, that Dr. Bancroft (who is named in the letter) could not, on account of his own affairs, have accepted even a primary appointment. I think it evident, that no appointment could have succeeded without a much greater sum of money.
I am happy to find that Mr. Barclay's mission has been attended with complete success. For this we are indebted, unquestionably, to the influence and good offices of the court of Madrid. Colonel Franks, the bearer of this, will have the honor to put into your hands the original of the treaty, with other papers accompanying it. It will appear by these, that Mr. Barclay has conducted himself with a degree of intelligence and of good faith, which reflects the highest honor on him.
A copy of a letter from Captain O'Bryan to Mr. Carmichael, is also herewith enclosed. The information it contains will throw farther light on the affairs of Algiers. His observations on the difficulties which arise from the distance of Mr. Adams and myself from that place, and from one another, and the delays occasioned by this circumstance, are certainly just. If Congress should propose to revive the negotiations, they will judge whether it will not be more expedient to send a person to Algiers, who can be trusted with full powers; and also whether a mission to Constantinople may not be previously necessary. Before I quit this subject, I must correct an error in the letter of Captain O'Bryan. Mr. Lambe was not limited, as he says, to one hundred, but to two hundred dollars apiece for our prisoners. This was the price which has been just paid for a large number of French prisoners, and this was our guide.
I
