Thomas Jefferson Papers

From Thomas Jefferson to Francis Hopkinson, 3 January 178[6]

To Francis Hopkinson

Paris Jan. 3. 1785 [i.e. 1786]

Dear Sir

I wrote you last on the 25th. of Sep. since that I have received yours of Oct. 25. inclosing a duplicate of the last invented tongue for the harpsichord. The letter inclosing another of them and accompanied by newspapers, which you mention in that of Oct. 25. has never come to hand. I will embrace the first opportunity of sending you the crayons. Perhaps they may come with this, which I think to deliver to Mr. Bingham who leaves us on Saturday for London. If on consulting him I find the conveyance from London incertain, you shall receive them by a Mr. Barrett who goes from hence for New York next month. You have not authorised me to try to avail you of the new tongue. Indeed the ill success of my endeavors with the last does not promise much with this. However I shall try. Houdon only stopped a moment to deliver me your letter, so that I have not yet had an opportunity of asking his opinion of the improvement. I am glad you are pleased with his work. He is among the foremost, or perhaps the foremost artist in the world.

Turning to your Encyclopedie, Arts et metiers, tome 3. part. 1. pa. 393. you will find mentioned an instrument invented by a Monsr. Renaudin for determining the true time of the Musical movements Largo, Adagio &c. I went to see it. He shewed me his first invention. The price of the machine was 25. guineas; then his second, which he had been able to make for about half that sum. Both of these had a mainspring and a balance wheel for their mover and regulator. The strokes were made by a small hammer. He then shewed me his last which is moved by a weight and regulated by a pendulum, and which costs only two guineas and a half. It presents in front a dial plate like that of a clock on which are arranged in a circle the words Largo, Adagio, Andante, Allegro, Presto. The circle is moreover divided into 52 equal degrees. Largo is at 1, Adagio at 11, Andante at 22, Allegro at 36 and Presto 46. Turning the index to any one of these, the pendulum (which is a string with a ball hanging to it) shortens or lengthens so that one of it’s vibrations gives you a crotchet for that movement. This instrument has been examined by the Academy of music here, who are so well satisfied of it’s utility that they have ordered all music which shall be printed here in future, to have the movements numbered in correspondence with this plexichronometer. I need not tell you that the numbers between two movements, as between 22. and 36. give the quieter or slower degrees of the movements, such as the quick Andante, or moderate Allegro. The instrument is useful, but still it may be greatly simplified. I got him to make me one, and having fixed a pendulum vibrating seconds, I tried by that the vibrations of his pendulum according to the several movements. I find the pendulum regulated to

Largo } vibrates {  52. } times in a minute.
Adagio  60.
Andante  70.
Allegro  95
Presto 135

every one therefore may make a chronometer adapted to his instrument. For a harpsichord the following occurs to me. In the wall of your chamber, over the instrument drive 5. 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 52 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 60 times in a minute, fix the third for 70. vibrations &c. the cord always hanging over No. 1. as the center 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 peice. I have been thus particular on the supposition you would fix one of these simple things for yourself.

You have heard often of the metal called platina, to be found only in S. America. It is insusceptible of rust as gold and silver are, none of the acids affecting it except 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 of the metal. The experiment has been lately tried here by the Abbé Rochon (whom I formerly mentioned to Mr. Rittenhouse as having discovered that lenses of certain natural Chrystals 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 it’s reflection. This article is intended for Mr. Rittenhouse.

Good qualities are sometimes misfortunes. (Do not cry out Heresy as yet.) I will prove it from your own experience. You are punctual; and 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 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 Colden wrote a very small pamphlet on the subjects of attraction and impulsion, a copy of which he sent to Monsr. 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 N. Jersey may have preserved a copy.

In the king’s cabinet of Natural history of which M. de Buffon has the superintendance, I observed that they had neither our growse nor our pheasant. These I know may be bought in the market of Philadelphia on any day which they are in season. Pray buy the male and female of each, and employ some of the Apothecary’s boys to prepare them and pack them. Methods may be seen in the preliminary discourse to the 1st. volume of Birds in the Encyclopedie, 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 procure 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 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 million of 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 en Europe generally. From the smallest to the highest commissions I will execute with zeal and punctuality, 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 expences attending my commissions and favor me with it every now and then and I will replace it. My daughter is well and retains an affectionate remembrance of her antient 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 & servt.,

Th: Jefferson

P.S. What is become of the Lunarium for the king? My daughter begs the benefit of your cover for the inclosed letter.1

PrC (DLC). RC (Edward Hopkinson, Jr., Philadelphia, 1947); final page only. Noted in SJL as sent “viâ London by Mr. Bingham.” The enclosed letter from Martha Jefferson has not been identified.

Cadwallader Colden’s very small pamphlet was An Explication of the First Causes of Action in Matter, and, of the Cause of Gravitation, New York, James Parker, 1745 (see note to Sabin, description begins Joseph Sabin and others, Bibliotheca Americana. A Dictionary of Books Relating to America description ends No. 14267, which states that Buffon had caused this pamphlet to be translated). The lunarium was the orrery that TJ proposed to have Rittenhouse make for presentation to Louis xvi by the American Philosophical Society; see Vol. 6: 418–9.

1This sentence appears in RC only, having been written after PrC was made.

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