11 - The Marsili institution and Bolognese Astronomy at the beginning of the XVIIIth century.

Luigi Ferdinando Marsili (1658-1730) was born in 1658, the cadet son of one of the most illustrious senatorial families in Bologna. His uncle, Cesare Marsili, had corresponded with Galileo. The young count studied mathematical sciences with Giovanni Alfonso Borelli (1608-1679), astronomy with Geminiano Montanari and anatomy with Marcello Malpighi. He then chose a military career enrolling in the imperial army where he rapidly rose to the rank of colonel and assumed the duties of a military strategist, taking part in the campaign that ended in the rout of the Turks outside Vienna.

It was in this period that he began to grow concerned over how things were going in his native city.

He was convinced that only technical superiority, in military strategy, had saved Europe from the Turks and that this technical superiority was closely linked to the scientific and technological superiority the european countries enjoyed over the Turkish empire.

Bologna on the other hand appeared to be languishing in veneration of its ancient institutions. The privileges of the arts corporations acted as a brake on technical modernization, those of the University on cultural modernization. When Cassini returned to Bologna in 1695 to make some observations with the meridian in San Petronio he found astronomical studies in a complete state of abandon.Marsili, at first in a private capacity, tried to remedy this situation by opening his mansion - full of natural history collections, physics apparatus, astronomical instruments and books that he had amassed over the years - to any enterprising youngster who wanted to further his knowledge in the field of experimental sciences.

At the same time he commissioned Eustachio Manfredi, then just 28 and lecturer from two years in Astronomy at the University, to erect an observatory tower on the roof of the ancestral home.

All this took place at the beginning of the new century. The Marsili institution acquired characteristic features from the outset. It was not an academy like those in London and Paris whose operations centred around periodic meetings during which scientific innovations were discussed and the academicians made their own contributions to inventions and discoveries; it was more a place which provided actual instruments for work, where operations were of a more permanent character and where the work of the people involved became steadily more systematic and organized. Marsili at that time was moreover away from Bologna and could only follow his institution from afar with general directives and advice; advice which, from certain points of view, forced it to acquire a measure of self-sufficiency.

Marsili did in fact have to take part, as General, in the war that broke out in 1701 between France and Austria for succession to the throne of Spain and it was only in 1708 that he was able to return to Bologna for a brief stay.

Astronomy had a special role in the Marsili institution. The new academies, especially the Académie Royale, had very close ties with "power". They were in fact instruments, not to mention ornaments, of monarchic authority. Astronomy was the most explicit example of this for the immediate effects already mentioned. Viceversa, astronomy was also the first of the experimental sciences to have to give up its artisanal framework for a more collective approach and to require substantial institutional support. At the beginning of the XVIIIth century the astronomical community was already well organized, with a well defined programme and regular cultural exchanges; its institutionalization thus proved to be remarkably simple, not to mention productive.

There is much evidence that points to the fact that, from the very beginning, Marsili wanted to do for Italy what the Paris Académie was doing for French geography. Though the programme was never carried through, numerous traces of it remain (69) (70) and help shed light on the origin of the Ephemerides Bononienses, that we shall have occasion to say more about later.

Re the beginnings of the Marsili institution, in a 1780 revision of the guide to the Bologna Institute of Sciences, which had been drawn up in 1751 by Giuseppe Gaetano Bolletti, we read:


"In the midst of this huge apparatus it seemed that Astronomy still wanted some help. What was missing in fact was an observatory tower for astronomical observations. Marsili...wanted the Observatory to be built at his own expense...two whole years went by before the Observatory was completed, the necessary instruments installed, and everything ordered" (71).

As we have already seen, the young Bolognese Eustachio Manfredi, renowned not just as an astronomer but as a promoter of the Accademia degli Inquieti, was given charge of the new building project, along with Vittorio Stancari (1678-1709) whose association with Manfredi went back to their adolescence together.

This academy had started off as nothing more than a boys’ game, when Manfredi was little more than fifteen, but had gradually been consolidated and grew into an important cultural institution, a point of reference for Bologna’s brightest students. Its existence was probably one of the factors inducing Marsili to undertake his project. From 1705 it did in fact meet at the Marsili villa.

Eustachio Manfredi (1674-1739) was born in Bologna in 1674 and Vittorio Stancari in 1678, by when Cassini had long since left the city. When they began to grow interested in astronomy they were unable to find a teacher in Bologna and were forced to rely on themselves. In his eulogy to Manfredi which he read to the Paris Académie in 1739, Bernard Le Bovier de Fontenelle wrote:

"The famous Bologna Meridian, designed and built in 1655 by the deceased Mr Cassini, this wonderful gnomon, the biggest and consequently the most useful astronomy has ever had, and could ever hope to have, lay abandoned, neglected in the church of San Petronio; there were not the astronomers for this beautiful instrument. Mr Manfredi, just 22, decided to use it, to spare his country this shame, and was helped by Mr Stancari, his dear and worthy friend. They set about studying astronomy books together, immediately began spending the nights in observations with the best instruments they could have obtained from their manufacturers and were practically the first in Italy to use a clock with a cycloidal pendulum." (72)

Fontanelle’s story is backed up by papers preserved in the Archives of the Department of Astronomy in Bologna. These in fact include a series of Manfredi’s and Stancari’s notebooks which contain observations carried out at the meridian of San Petronio (73). The oldest of these begins with an observation of August, 3 1697, when Manfredi was 23.

Between 1698 and 1702, besides continuing with the observations at the meridian of San Petronio, Manfredi, his three brothers and Stancari somehow organized a small observatory in the home of the former. They had an astronomical sextant built by the same Stancari consisting of a wooden sector - 30° aperture and 8 foot (3 m) radius - which was soon fitted with telescopic sights. The instrument’s accuracy was around one arcminute. They also had various telescopes, the largest of which had a focal length of 13 feet (5 m), though of somewhat poor optical quality.

The interests of Manfredi and Stancari clearly emerge from the observation notebooks and waste books of those years (74) and from the appendix to Stancari’s Schedae Matematicae published posthumously in 1713 by Manfredi, collecting the inedited works of Stancari and the observations the two of them made in those early years. Manuscript copy of the Schedae Mathematicae... can be found in the Archives of the Department of Astronomy in Bologna.(75)

At first, they set about making systematic observations of relative star positions with the ambitious aim of mapping the sky in a similar way to Flamsteed in England. They soon had to face the fact however that the wooden instruments Stancari built were not stable enough for work of this nature and so they limited themselves to studying the movements of the planets. From 1699 they abandoned the sextant in favor of a telescope equipped with micrometric reticle which together with a good clock enabled them to carry on their observations of planet motion. They also observed eclipses of the Moon, the Sun, those of the satellites of Jupiter, and lunar occultations, with the aim of determining as accurately as possible the geographic position of Bologna. They also observed two comets during 1702.

A letter by Marsili dated Brisac March 20, 1703, bears witness to his intention of employing Manfredi in his service as soon as he left the Collegio dei Poeti and finding him a suitable position.(76)

Manfredi and Stancari therefore were given carte blanche in overseeing the building of the Marsili Observatory.

In a letter to Manfredi, dated Bologna September 1, 1703, Stancari declares himself: "very satisfied with Mr Co. Filippo (brother of Marsili). He granted me this morning bread, wine and twelve baiocs a day, ten of which he believes should be spent on something to eat with the bread, one on fruit, and the other for the candle".(77)

The construction of the observatory rose above the granaries of the Marsili Mansion, in the far North, on what is today via d’Azeglio. The report of the master builder engaged in the project is still today preserved in the Archives of the Department of Astronomy in Bologna, together with a plan (78). The idea of the building is somewhat similar to that of the Torretta, or turret, which lies over the present-day university Specola: a construction with plenty of windows, octagonal in this case, placed in the centre of a large terrace. This construction no longer exists, the Marsili Mansion having been refashioned a few years ago. The architectonic volume can perhaps be guessed at from a sort of roof-terace that lies over the north-west corner of the building. Marsili sent from Vienna, where he was then posted, drawings of "large iron instruments" built in Nuremburg, saying that if they were to everyone’s liking "they would be solicitously ordered".

The instruments were instead ordered from the shop of the family of craftsmen in Rome, the Lusvergs, and were: a movable astronomical quadrant [file 11], "similar but more perfected" than the one owned by Marsili, a mural semicircle [file 16] and a 3 foot (just over 1 m) telescope for micrometric observations. These instruments (with the exception of the telescope which was never built) are listed in a hand-written note of Manfredi to the fol 1v of the first volume of the register of observations carried out in the Marsili Observatory, volumes which are today preserved in the Archives of the Department of Astronomy in Bologna. A second movable quadrant was later ordered from Lusverg [file 12] and all these instruments were then given to the Specola of the Istituto delle Scienze (currently exhibited in the museum); their history can be reconstructed from the documents pertaining to that institution.

The observatory also had various English, French and even Bolognese clocks. There were also numerous telescopes, including those of Campani, excellent for the period, with their accessories for setting the instrument up and using it [files 27, 28, 29, 30].

The Specola had cost Count Marsili 2400 scudi to build (79).

Manfredi carefully examined all the instruments, accurately making all the corrections necessary to measurements at the time of the observations. The scale of Lusverg’s second quadrant seemed much better and finer cut than the first and on 10 December 1703 the instrument began to be used. With its help the method of using "corresponding elevations" to obtain the transit time of the stars along the meridian was adopted.

When a quadrant is used to determine the transit time across the meridian of celestial bodies by the method of corresponding elevations, the only thing that counts is being able to reposition the instrument at the same elevation; for all other uses, however, the important thing is the accuracy of the scale cut on its limb and the precision with which it has been rectified i.e. the precision of the reading of the scale when the instrument is pointing towards the zenith or the horizon.

An examination of the records shows that errors greater than two seconds of time occurred rarely in this type of measurement. Taking into account the radius of the quadrant, this indicates that the estimation for the position of the plumb-line on its graduated limb must have had an accuracy greater than 1/20 of a millimetre and that the clock which was used must have been accurate to one second in several hours. The precision of the scale of Lusverg’s instruments and the quality of their rectification can be inferred from the different computations of latitude of the site of observation obtained with them. The results lead to the conclusion that the markings on the limbs were accurate to 1/100 of a millimetre, not that much inferior, in terms of quality, to the more celebrated English instruments of mid-century (80).

With the main instrument, the mural semicircle, it was possible to observe the transit across the meridian of the stars. There were however some difficulties due to the positioning of the instrument along the meridian and its planarity. In order for the telescope, sliding on its graduated limb, not to deviate more than a fraction of a second, i.e. 5 or 10 arcsecs, from a great circle, the plane of the instrument would have had to be accurate to a few hundredths of a millimetre. To be able to use it for meridian observations, deviation from the meridian had to be calculated, elevation by elevation.

To this end, the string meridian was introduced in April 1706 (file 3). This is an instrument as simple as it is accurate: it consists of a thin metal wire stretched along the meridian and tested by the method of corresponding elevations. The image of the solar disk, projected through a small hole in the south wall, makes it possible to compute the moment of the Sun’s passage at local noon by estimating the mean time between the moment when the wire’s shadow, illuminated by the Sun on a piece of white card placed under the wire itself, enters and when it leaves. Error was no more than one second of time, which meant the position of the mural semicircle could be verified by observing daily the differences between the transit times of the Sun along the meridian and the telescope of the semicircle.

The one or two second differences between these transit times spurred Vittorio Stancari to design a completely new instrument: the so-called transit telescope which would have allowed the recording of observations free of any irregularity along the meridian. Unfortunately, this instrument - which was conceived by Stancari at the same time as Ole Römer and Edmund Halley (1656-1724) and whose support is all that has been found (file 18) - never got past the first stages: Vittorio Stancari died on 28 March 1709 of consumption at the early age of thirty, as his friend Manfredi sadly noted in the records.

Pursuing their early studies, the two astronomers had then made a whole series of observations of eclipses, sun spots and comets, but one problem remained foremost in Manfredi’s mind as it did in many other astronomers of the period: the observation of yearly movements of the "fixed" stars. An annual variation in the apparent motion of the stars around the Earth - the so-called "stellar parallax" - would in fact have given irrefutable proof of the revolutionary motion of the Earth around the Sun, thus providing observational verification of the Copernican system, as Aristarchus of Samos had intuited 2000 years before.

The Marsili institution was already seven years old when Marsili began to think of making it permanent, by donating to the City the collections, the instruments and that part of the mansion which housed it. When the other members of his family learnt of his intentions, they formally opposed the idea, at least as regards the transfer of part of the house, saying he had no right to damage the interests of his future heirs.

The Count took this opposition as an affront and:

"at once cleared everything from the house; he took himself to live in another place; the Academies closed and everything was packed to transport it elsewhere".(81)

And that was the end of the observatory at Palazzo Marsili. The observation records break off suddenly on May 28, 1709, with the following note written by Eustachio Manfredi, which is also a promise:

"The semicircle is removed from its mount and moved along with the rest of the astronomical equipment until a new building is put up."(82)

  1. - G. Fantuzzi: 1770, Memorie della Vita del Generale Co: Luigi Ferdinando Marsili, Bologna, p.281 (lettera IX, di Marsili al canonico Trionfetti datata dalla selva Belinaz il 14 novembre 1696) e p. 319 (lettera XXIX, di Eustachio Manfredi a Marsili in Roma del 30 agosto 1711).
    J. Stoye: 1994, Marsigli's Europe. 1680-730, Yale University Press, New Haven & London.
    W. Tega (a cura di): 1986, Anatomie accademiche: I. I Commentari dell'Accademia delle Scienze di Bologna, Il Mulino, Bologna.
    W. Tega (a cura di): 1987, Anatomie accademiche: II. L'Enciclopedia scientifica dell'Accademia delle Scienze di Bologna, Il Mulino, Bologna.
    A. Angelini (a cura di): 1993, Anatomie accademiche: III. L'Istituto delle Scienze e l'Accademia, Il Mulino, Bologna.
  2. - V.F. Stancari: lettere al Manfredi datate da Bologna il 4 e 9 novembre 1704, Archivio Dipartimento di Astronomia, busta XXXVI.
  3. - Notizie dell'origine, e progressi dell'Istituto delle Scienze di Bologna e sue Accademie...: 1780, Bologna, p. 10.
  4. - B. Le Bovier de Fontenelle: 1739, Eloge de Mr. Manfredi, Hist.Ac.Roy.Sciences (ed. di Amsterdam), p.86.
    "La famosa Meridiana di Bologna, ideata e realizzata nel 1655 dal defunto signor Cassini, questo meraviglioso gnomone, il più grande e di conseguenza il più utile che l'astronomia abbia mai avuto, e che abbia mai potuto desiderare, giaceva abbandonata, trascurata nella chiesa di San Petronio; mancavano degli astronomi a questo bello strumento. Il signor Manfredi, appena ventiduenne, si risolse a utilizzarlo, per togliere alla sua patria questa specie di macchia, e fu aiutato dal signor Stancari, suo caro e degno amico. Essi si misero a studiare insieme dei libri d'astronomia, subito si misero a trascorrere le notti osservando con i migliori strumenti che avevano potuto ottenere dai loro costruttori e furono praticamente i primi in Italia a utilizzare un orologio a cicloide."
  5. - Archivio Dipartimento di Astronomia di Bologna, busta I
  6. - Archivio Dipartimento di Astronomia di Bologna, busta I
  7. - Stancari Vittorio Francesco: 1713, Schedae Mathematicae post eius obitum collectae eiusdem Observationes Astronomicae, Bologna. Copia manoscritta delle Schedae Mathematicae ... si trova presso l'Archivio del Dipartimento di Astronomia di Bologna.
  8. - G. Fantuzzi: op. cit., p. 307. Una lettera di Marsili datata da Brisac il 20 marzo 1703 ci testimonia la sua intenzione di assumerlo al proprio servizio non appena egli fosse uscito dal Collegio dei Poeti, e la preoccupazione di trovargli una sistemazione adeguata.
  9. - V. F. Stancari: lettera a Manfredi, datata Bologna, 1 settembre 1703, in cui si afferma "soddisfattissimo del Sig. Co. Filippo (fratello di Marsili). Egli mi ha accordato questa mattina pane, vino e dodici baiocchi il giorno, dieci dei quali suppone egli da spendersi per il companatico, uno in frutta, e l'altro per la candela", Archivio Dipartimento di Astronomia di Bologna, busta XXXVI.
  10. - Archivio Dipartimento di Astronomia di Bologna, busta II.
  11. - G. Fantuzzi: op.cit., p. 224.
  12. - A. Braccesi: 1978, Gli inizi della specola di Bologna, Giornale di Astronomia, 4, p. 327.
  13. - G. Fantuzzi: op.cit., p. 226.
  14. - "Il semicerchio viene rimosso dalla sua sede e con esso si trasferisce tutta la strumentazione astronomica in attesa dell'edificazione di una nuova sede".