In the wall of your chamber, over the instrument, drive five little brads, as, 1, 2, 3, 4, 5, in the following manner. Take a string with a bob to it, of such length, as, that hung on No. 1, it shall vibrate fifty-two times in a minute. Then proceed by trial to drive No. 2, at such a distance, that drawing the loop of the string to that, the part remaining between 1 and the bob, shall vibrate sixty times in a minute. Fix the third for seventy vibrations, &c.; the cord always hanging over No. 1, as the centre of vibration. A person playing on the violin may fix this on his music-stand. A pendulum thrown into vibration will continue in motion long enough to give you the time of your piece. I have been thus particular, on the supposition that you would fix one of these simple things for yourself.
You have heard often of the metal called platina, to be found only in South America. It is insusceptible of rust, as gold and silver are, none of the acids affecting it, excepting the aqua regia. It also admits of as perfect a polish as the metal hitherto used for the specula of telescopes. These two properties had suggested to the Spaniards the substitution of it for that use. But the mines being closed up by the government, it is difficult to get the metal. The experiment has been lately tried here by the Abbe Rochon (whom I formerly mentioned to Mr. Rittenhouse, as having discovered that lenses of certain natural crystals have two different and uncombined magnifying powers), and he thinks the polish as high as that of the metal heretofore used, and that it will never be injured by the air, a touch of the finger, &c. I examined it in a dull day, which did not admit a fair judgment of the strength of its reflection.
Good qualities are sometimes misfortunes. I will prove it from your own experience. You are punctual; and almost the only one of my correspondents on whom I can firmly rely, for the execution of commissions which combine a little trouble with more attention. I am very sorry however that I have three commissions to charge you with, which will give you more than a little trouble. Two of them are for Monsieur de Buffon. Many, many years ago, Cadwallader Golden wrote a very small pamphlet on the subjects of attraction and impulsion, a copy of which he sent to Monsieur de Buffon. He was so charmed with it, that he put it into the hands of a friend to translate, who lost it. It has ever since weighed on his mind, and he has made repeated trials to have it found in England. But in vain. He applied to me. I am in hopes, if you will write a line to the booksellers of Philadelphia to rummage their shops, that some of them may find it. Or, perhaps, some of the careful old people of Pennsylvania or New Jersey may have preserved a copy. In the King’s cabinet of Natural History, of which Monsieur de Buffon has the superintendence, I observed that they had neither our grouse nor our pheasant. These, I know, may be bought in the market of Philadelphia, on any day while they are in season. Pray buy the male and female of each, and employ some apothecary’s boys to prepare them, and pack them. Methods may be seen in the preliminary discourse to the first volume of Birds, in the Encyclopédie, or in the Natural History of Buffon, where he describes the King’s cabinet. And this done, you will be so good as to send them to me. The third commission is more distant. It is to precure me two or three hundred paccan nuts from the western country. I expect they can always be got at Pittsburgh and am in hopes, that by yourself or your friends, some attentive person there may be engaged to send them to you. They should come as fresh as possible, and come best, I believe, in a box of sand. Of this, Barham could best advise you. I imagine vessels are always coming from Philadelphia to France. If there be a choice of ports, Havre would be the best. I must beg you to direct them to the care of the American consul or agent at the port, to be sent by the Diligence or Fourgon. A thousand apologies would not suffice for this trouble, if I meant to pay you in apologies only. But I sincerely ask, and will punctually execute, the appointment of your chargé des affaires in Europe generally. From the smallest to the highest commission, I will execute with zeal and punctually, in buying, or doing any thing you wish, on this side the water. And you may judge from the preceding specimen, that I shall not be behind hand in the trouble I shall impose on you. Make a note of all the expenses attending my commissions, and favor me with it every now and then, and I will replace them. My daughter is well, and retains an affectionate remembrance of her ancient patroness, your mother, as well as of your lady and family. She joins me in wishing to them, and to Mr. and Mrs. Rittenhouse and family, every happiness. Accept, yourself, assurances of the esteem with which I am, Dear Sir,
your friend and servant,
Th: Jefferson.
P.S. What is become of the Lunarium for the King?
LETTER CXLVIII.—TO GENERAL WASHINGTON, January 4, 1786
TO GENERAL WASHINGTON.
Paris, January 4, 1786.