1791 - Captivating Scientific Letter from Italy’s Premier 18th Century Astronomer, Barnaba Oriani, thanking the Prussian Ambassador from the Court of Saxony to the King of Great Britain, the Count of Brühl, for his help in getting leading English Astronomers and Instrument Makers: Ramsden, Troughton and Smeaton, to send him specialized astronomical, navigational, celestial mechanics and microscope equipment. An incredibly detailed account of scientific instruments at the close of the 18th century.

Italian Astronomer corresponds with German Ambassador to England in 1791

Scientific correspondence, written in French, between leading astronomer Barnaba Oriani of the Brera Observatory in Milan and German Ambassador Count Hans Moritz von Brühl in London, an astronomy enthusiast and gifted chess-player. Oriani writes to Count Brühl thanking him for his aid in obtaining a Meridian Circle Quadrant, an instrument used for observing the time a star takes to pass through a meridian, at the same time measuring its angular distance from the zenith. This instrument is still at the Brera Observatory in Milan. The concept of having a fixed instrument on a plane of the meridian was envisaged by ancient astronomers and suggested by Ptolemy, but it was Tycho Brahe who constructed the first large Meridian Quadrant. Oriani makes reference to Jesse Ramsden, inventor of the ‘dividing engine’, which combined the use of a microscope and a micrometer, and inventor of the Ramsden achromatic eyepiece. Oriani writes of Edward Troughton, an English inventor and instrument maker, known for his telescopes and other astronomical inventions, whose designs include the pillar sextant. It is Oriani’s wish that Troughton build the Zenithal Sector for the Brera Observatory, however, we are informed that, regretfully, this particular instrument was never delivered. Both Ramsden and Troughton were recipients of the Copley Medal, the highest award given by the Royal Society in London. The letter also mentions John Smeaton, also a Copley medalist, with reference to his current work, who is considered the father of civil engineering. This is a fantastic letter that ties together several notable 18th century astronomers and scientists and their work using the Meridian Circle Quadrant as well as reference to their contemporary astronomical tools and studies.

The original letter is written in French, but has been translated to English.

Item Ref:  BSL - Oriani 1791

Please click Page images to enlarge - text in French

Text of Letter page 1

Text of Letter page 2

Text of Letter page 3

Red Wax Seal from the reverse of the cover

Milan April 26th Postal Mark

British Postal Mark
Bishops Mark indicating May 9th as the date of receipt of the letter in London

Reverse of Cover

Below is an extensive Historical Note including Transcription and Translation as well as Biographical Information on the major parties and instruments mentioned in the letter.

Barnaba Oriani (1752–1832) was born in Carignano, Italy and studied at the College of San Alessandro in Milan, which was supported by the Barnabites, who he later joined. Oriani was ordained priest at the age of 23. His lifelong passion was astronomy and he was appointed to the staff at the Brera Observatory in Milan in 1776, became assistant director in 1778 and director in 1802. In 1778 he began to publish the dissertations on astronomical subjects which appeared in the "Effemeridi di Milano" during the next fifty-two years. Some of his work includes observation of “nebulous stars” and the orbit calculation of the planet Uranus, which he proved to be circular and not parabolic. Oriani also worked on similar calculations for Saturn and Jupiter. In 1784 some of his work was published in Bode’s Astronomical Yearbook. His work soon attracted considerable attention, and in 1785 a notable memoir containing his calculation of the orbit of Uranus and a table of elements for that planet won for him a prominent place among the astronomers of his time. He was admitted to membership in numerous learned societies, and offered the position of professor of astronomy at Palermo, which, however, he did not accept. In the following year he traveled throughout Europe at the expense of the state, visiting the chief observatories. In 1802 he was also appointed cartographer for the new Italian Republic and calculated the arc of the meridian between Rome and Rimini.

When Napoleon set up the Republic in Lombardy, Oriani refused absolutely to swear hatred towards monarchy; the new government modified the oath of allegiance in his regard, retained him in his position at the observatory, and made him president of the commission appointed to regulate the new system of weights and measures. When the republic was transformed into the Napoleonic kingdom, Oriani received the decorations of the Iron Crown and of the Legion of Honour, was made count and senator of the kingdom. He was a devoted friend of the Theatine monk Piazzi, the discoverer of Ceres, and for thirty-seven years cooperated with him in many ways in his astronomical labours. Besides his constant contributions to the "Effemeridi di Milano", he published a series of important memoirs on spherical trigonometry (Memorie dell' Istituto Italiano, 1806-10) and the "Istruzione suelle misure e sui pesi" (Milan, 1831). Oriani died in Milan in 1832. In 1988 a meteor was named after him in his honor.

Count Hans Moritz von Brühl (1736-1809) was born in Wiederau Germany, the son of Count Heinrich von Brühl. He served as a Colonel in the French service and would later become the Minister of Saxony in Germany and the Ambassador to England. He married the beautiful and bright Margarethe Schleierweber, the daughter of a French corporal and they had a son, Karl Friedrich Moritz Paul von Brühl (1772-1837). Brühl was a patron of music and had an interest in astronomy, building his own observatory and writing astronomical papers, as referenced by Oriani in his letter. He was a talented chess player in the London Chess Club, his friend and fellow chess player François André Philidor wrote the book L’analyse du jeu des Echecs, and dedicated it to his friend the Count.

Jesse Ramsden (1735–1800) was born near Halifax in West Yorkshire, England. In 1755 he relocated to London where he worked as an apprentice to a mathematic instrument maker. He would go on to become a renown instrument manufacturer in the 1770s and 1780s. Ramsden’s most important invention, called a ‘dividing engine’, was an instrument used in calculating angles by using a micrometer and a microscope. Ramsden is also known for inventing the achromatic eyepiece, which bears his name. In 1785 General William Roy of the Royal Engineers commissioned a Theodolite, this is also referenced in Oriani's letter, a fundamental instrument used for surveying and map-making, which was used to calculate the distance between Greenwich, London and Paris. Ramsden was awarded the Copley Medal, the highest award given by the Royal Society in London, for his participation in this project. He died in 1800 in Brighton, Sussex, England.

Edward Troughton (1753-1835) was a top British instrument maker who was renown for his telescopes and other astronomical instruments. In 1779 he and his brother John teamed up to become the top inventors and manufacturers of navigational, surveying and astronomical instruments in Britain. Some of his inventions included a design for the 'pillar' sextant, which was patented in 1788, the dip sector, the marine barometer and the reflecting circle, built in 1796. Stephen Groombridge used Troughton’s work on the Groombridge Transit Circle to create his star catalogue. In 1809, the Royal Society awarded him the Copley Medal for his work on the paper: An account of the method of dividing astronomical and other instruments by ocular inspection in the Philosophical Transactions of the Royal Society. Because of his health, Troughton took on William Simms as a partner in 1826 and the company became Troughton & Simms. Troughton was colorblind and died at his home on Fleet Street in London in 1835. He apparently never built nor delivered the Zenithal Sector for which Oriani had hoped, perhaps because he scientific instrument budget was upended by the cost, £900 sterling!, of acquiring the Meridian Circle Quadrant.

John Smeaton (1724–1792) was a civil engineer – indeed, he is often regarded as the "father of civil engineering" – responsible for the design of bridges, canals, harbours and lighthouses. He was born at Austhorpe near Leeds, West Yorkshire, England. He joined his father's law firm, but then left to become a mathematical instrument maker (working with Henry Hindley), developing, among other instruments, a pyrometer to study material expansion and a whirling speculum or horizontal top (a maritime navigation aid). He was also a more than capable mechanical engineer and an eminent physicist. He was associated with the Lunar Society. He was elected a Fellow of the Royal Society in 1753, and in 1759 won the Copley Medal for his research into the mechanics of waterwheels and windmills. His paper addressed the relationship between pressure and velocity for objects moving in air, and his concepts were subsequently developed to devise the 'Smeaton Co-efficient'.

Recommended by the Royal Society, Smeaton designed the third Eddystone Lighthouse (1755-59). He pioneered the use of 'hydraulic lime' (a form of concrete) and developed a technique involving dovetailed blocks of granite in the building of the lighthouse. Because of his expertise in engineering, Smeaton was called to testify in a court for a case related to the silting-up of the harbour at Wells-next-the-Sea in Norfolk in 1782. He is considered to be the first expert witness to appear in an English court. Highly regarded by other engineers, he contributed to the Lunar Society and founded the Society of Civil Engineers in 1771. He coined the term "civil engineers" to distinguish them from military engineers graduating from the Royal Military Academy at Woolwich. After his death, the Society was renamed the Smeatonian Society, and was a forerunner of the Institution of Civil Engineers, established in 1818.

Historical Note

This is the English translation of the letter:


The large Meridian Circle Quadrant has finally arrived in good condition, and as Your Excellency really wanted to contribute his recommendations of M. Ramsden and to have it finished sooner than I could ever have imagined, my colleagues and I send him our respectful thanks. It is true that it cost us a lot of money, but it is a treasure that we will always have, and in any case, the excessive price isn’t because of the artist but of the famous Imperial Consul and the Royal Songa, because only by a Hackney coach to go to Ramsden’s he made us pay 56 pounds sterling and another 30 pds. st. [£ sterling] for his deposit, etc. 50 pds. st. for transport from London to Genoa, and as much from Genoa to Milan, etc. When it will finally be in its place it will cost us more than 900 pds. st. This spending has taken away our hope this year to obtain the Zenithal Sector, but quod difertur non aufertur, we are still determined to have it constructed by Mr. Troughton, and we flatter ourselves that within the coming year we will have enough money in the Observatory account for this purchase. If Mr. Troughton has already begun this instrument or if he wants to start it without us first spending half of the fee, he will be paid in full once he has completed it. If, before he begins it, he wants half the fee, then he will have to wait several more months. But I hope that he will be confident enough to believe that we are in a position to pay him promptly when it is finished.

Everything that immediately has to do with the Ramsden Circle Quadrant is already take care of, as I already know nearly all of the pieces. But I still do not understand the usage of the pieces of wood that look like this [Illustration on page] which maybe have something to do with the verification of the instrument, I dare ask Your Excellency to ask Ramsden for a little word on the subject. It has been impossible until just now to obtain the slightest clarification by the intervention of Mr. Songa, and consequently they are still useless. I had also asked Mr. Ramsden to send us some silver escort wire to put the micrometers back into place and hang it, because it was broken by accident, and not only is there no more wire, but it is missing entirely, the one that holds the hanging one. I hope that if V.E. (Your Excellency) would nicely ask for some from Mr. Ramsden, we will finally obtain what we are missing.

I offer my compliments to Your Excellency on the beautiful instruments he has just obtained; with a well-divided ring and an excellent landscape instrument he can brag about having a complete observatory where one can make all sorts of observations. I think that Your Excellency can show his circle on the parallactic machine, to more easily observe outside of the meridian. General William Roy had at his house a large Theodolite, that could be instantly placed between the two ends of a parallel axis and that of the Earth, and it became a pretty parallactic machine. Smeatons’s pendulum with a glass rod is extremely regular, and I would really like, with Your Excellency's permission to publish its progress in the next Ephemerides. If Your Excellency has other observations that he would like to give to the Italian Astronomers, I send him my most humble thanks in advance.

One of my friends commissioned me to procure for him one of the best microscopes and several other articles. I am writing directly to Mr. Adams by sending him a money order of 48 pds. st. In the same letter I ask him to buy me an artificial horizontal (only the black glass) for mine at either Nairne’s or Haay’s, because the one that Your Excellency sent me with Troughton’s sextant, is broken. I ask him to pick the best one, and to assure it, I ask him to put it to the test, and in the case that he doesn’t know any astronomers that have a good sextant and enough skill for this experiment, I tell him to address himself to Your Excellency in the persuasion that he will be kind enough to make the decision.

I have the honor of being with much esteem and the most profound respect
of Your Excellency

The very humble and obedient servant

Milan this 23 April 1791

This is the French transcription of the letter:


Le grand Quart de Cercle Mural est enfin arrivé en très bon état, et comme Votre Excellence a bien voulu contribuer par ses recommandations près de M. Ramsden à le faire achever plus tôt que je n’aurois (sic) cru, je lui fais mes respectueux remerciemens (sic) et ceux de mes Collègues. Il est vrai qu’il nous coûte beaucoup d’argent, mais c’est toujours un trésor que nous possédons, et d’ailleurs la faute du prix excessif ne vient pas de l’Artiste mais du célèbre Consul Impérial et royal Songa, car seulement en Hakney-coach pour aller chez Ramsden il nous a fait payer 56 livres sterl. et de plus 30 liv. st. pour sa provision etc. 50 liv. st. pour le transport de Londres jusqu’à Gênes, autant de Gênes à Milan, etc. Enfin lorsqu’il sera à sa place il nous coûtera au delà de 900 liv. st. Cette dépense nous a été l’espérance d’obtenir cette année le secteur Zenithal, mais quod difertur non aufertur, nous sommes toujours déterminés à le faire construire par M. Troughton, et nous nous flattons que dans l’année prochaine nous aurons dans la caisse de l’Observatoire assez d’argent pour cette emplette. Si M. Troughton a déjà commencé cet instrument ou s’il veut le commencer sans que nous déboursions d’abord la moitié du prix, il sera payé entièrement dès qu’il l’aura achevé. Si avant de le commencer il veut la moitié du prix, alors il faudra qu’il attende encore quelques mois. Mais j’espère qu’il aura assez de confiance pour nous croire en état de le payer promptement à la fin de l’ouvrage.

Tout ce qui regarde immédiatement le grand Quart de Cercle de Ramsden, est déjà arrangé, car je connoissois (sic) d’avance presque toutes les pièces. Mais j’ignore encore l’usage des pièces en bois de cette figure [illustrations] qui ont rapport peut-être à la vérification de l’instrument, j’ose donc prier Votre Excellence de demander à Ramsden un petit mot là-dessus. Il a été impossible jusqu’à cette heure d’en obtenir le moindre éclaircissement par l’entremise de M. Songa, et par conséquent elles restent ici sans utilité. J’avois (sic) aussi fait prier M. Ramsden de nous envoyer du fil d’argent d’escorte pour le remettre aux micrométres et à l’applomb (sic), lorsque par quelque accident il venoit (sic) à casser, et non seulement il n’y a pas ce surplus de fil, mais il manque entièrement celui même qui doit soutenir l’applomb (sic). J’espère que si V.E. veut bien nous faire la grâce d’en demander à M. Ramsden, nous obtiendrons enfin ce qui nous manque.

Je fais mille complimens (sic) à V.E. sur les beaux Instrumens (sic) qu’elle vient d’obtenir; Avec un cercle bien divisé et un excellent Instrument de paysages Elle peut se vanter d’avoir un Observatoire complet où l’on peut faire toutes sortes d’observations. Je crois que V.E. pourra monter son Cercle en machine parallatique (sic) pour observer plus aisément hors du méridien. Le feu Général Roy avoit (sic) chez lui un grand Teodolite, qui pouvoit (sic) dans un instant être placé entre les deux bouts d’un axe parallèle à celui de la Terre, et il devenoit (sic) une jolie machine parallatique (sic). La Pendule de Smeaton avec une verge de verre est extrêmement régulière, et je veux bien, avec la permission de V.E., en publier la marche dans les prochaines Ephemerides. Si V.E. a d’autres observations, dont elle veuille faire un cadeau aux Astronomes Italiens, je lui en ferai d’avance mes plus humbles remercimens (sic).

Un de mes amis m’a donné la commission de lui procurer un des meilleurs Microscopes et quelques autres articles. J’écris directement à M. Adams en lui envoyant une lettre de change de 48 liv. st. Dans la même lettre je le prie de m’acheter chez Nairne ou chez Haay un horizont artificiel (le verre noir seulement), car le mien, que V.E. m’a envoyé avec le sextant de Troughton, s’est cassé. Je le prie d’en choisir un des meilleurs et pour s’en assurer je lui recommande de le faire mettre à l’épreuve, et en cas qu’il ne connoisse (sic) aucun Astronome qui ait un bon Sextant et assez d’habilité pour cette expérience je lui dit de s’adresser à V.E. dans la persuasion qu’Elle aura la bonté de faire ce choix.

J’ai l’honneur d’être avec la plus grande estime et le plus profond respect
De Votre Excellence
Le très humble et très obéissant serviteur

Milan ce 23 Avril 1791


Document Specifications: The letter in one folded sheet forming four pages of batonne laid paper containing the watermark "G.A.S." within a scrolled crest and below are the initials "B.M.O." Each page measures 7¼" wide x 10¼" tall(185mm x 260mm). It is in Superb Condition with beautiful and extremely legible script handwriting and drawings. The letter is on three pages and the fourth page is the address panel to: His Excellency, the Count von Brühl, Minister Plenipotentiary of the Court of Saxony to the King of Great Britain, in London. It has a postal cancel of April 26th in red on the face and a Receiving mark in London by a black Bishop's Mark dated May 9th. It has an intact red wax seal. Text is in French but with  complete English Translation. An extraordinarily beautiful historic letter documenting the art and science of Astronomy, Celestial Mechanics, Navigation and Microscopes in the late 18th Century.


End of Item - BSL - Oriani 1791

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