Mem. S.A.It. Suppl. Vol. 22, 75c© SAIt 2013

Memorie della

Supplementi

Boscovich: his geodetic and cartographic studies

B. Crippa1, V. Forcella2, and L. Mussio2

1 Universita degli Studi di Milano, Dipartimento di Scienze della Terra “(Ardito Desio)”,Via Cicognara 7, 20133 Milano, e-mail: bruno.crippa@unimi.it

2 Politecnico di Milano, DIIAR Sezione Infrastrutture Viarie, Piazza Leonardo da Vinci,32, 20133 Milanoe-mail: valentina.forcella@mail.polimi.it;luigi.mussio@polimi.it

Abstract. The name of Ruggero Giuseppe Boscovich has many spellings: the CroatianBoscovic, linked to his Dalmatian origin, becomes Boscowich in German. RuggeroGiuseppe Boscovich lived and worked in many cities: Rome, Pavia, Venice, Paris, London,Warsaw, Saint Petersburg and Constantinople, where he carried out diplomatic missions.He was a Jesuit and studied mathematics, physics, astronomy, geodesy, and cartography.His studies in geodesy and cartography were developed in Italy: he measured the meridianbetween Rome and Rimini, he worked on the new map of the Papal State and he designedthe Brera Observatory. In the first part of the present work, we present Boscovich’s activitiesfrom a chronological point of view. In the second part, we focus on two specific arguments,related to geodesy and cartography: the new map of the Papal State and an attempt to rebuildthe associated triangulation.

Key words. Boscovich, Brera Observatory, geodetic activities

1. Introduction

An authoritative biography by an eminentscholar

The biography in the following paragraphis quoted from the “Enciclopedia ItalianaTreccani” and its on-line sources. These doc-uments were written by the astronomer LuigiGabba, who directed the Brera Observatory be-tween 1917 and 1922.

Ruggero Giuseppe Boscovich was born onMay 18, 1711 in Ragusa, Dalmazia and he diedon February 13, 1787 in Milan.

He studied at the “Collegium Ragusinum”and next at the “Collegium Romanum”.Boscovich entered the Jesuit company in 1726and he started teaching grammar and mathe-

matics at the “Collegium Ragusinum” beforehe became a priest.

His authoritativeness and his knowledge lethim to get many commissions. Some of themconcerned bridges, streets and canal systems,the stability of the dome of the Papal Basilicaof Saint Peter, the library in Vienna, the spireof the Milan Cathedral and the drainage of the“Paludi Pontine”.

Boscovich was delegated to claim therights of the Republic of Lucca in 1757 inVienna against the government of Tuscany.The controversy was about the draining of thelake Bientina.

Pope Benedictus XIV asked Boscovich andCristoforo Maire to measure the arc of merid-

76 Crippa et al.: geodetic and cartographic studies

Fig. 1. Starting point of the geodetic baseline along“Via Appia” from “Capo di Bove” to “Frattocchie”,near Rome

ian between Rome and Rimini. The aims ofthis work were two:

• the determination of the shape of the Earthand

• the adjustment of the map of the PapalState.

No information is available about the in-struments used by Boscovich. Anyway, a fewyears later, Canivet built a movable sextant inParis. Boscovich used it to measure azimuthalangles. Boscovich published the “De literariaexpedition per pontificiam ditionem ad dime-tiendos duos meridian gradus et corrigendammappam geographicam” in 1755.

Boscovich promoted the work of Liesganigin Hungary and the work of Beccaria inPiedmont, where the first meridian mea-surements were carried on by P. GiovanniBattista, who measured a meridian arc betweenMondovı and Biandrate.

Boscovich traveled around Europe: hestayed in Vienna (1758), in Paris (1759), inLondon (1760), in Warsaw, in St. Petersburgand in Constantinople (1761). In this last cityhe observed the transit of Venus across the Sun.He published the essay “Theoria PhilosophiaeNaturalis redacta ad unicum legem virium innatura existentium” in 1758 in Vienna. Thiswork relates to the atomistic theory of the uni-verse and it relates with the synthesis of the

Leibnizian dynamics and Newtonian mecha-nism. The interaction between the points isgoverned by the distances:

• for long distances, the law of universalgravitation governs the interactions,

• for short distances, the interactions are al-ternately attractive and repulsive, and

• for even shorter distances, the interactionsare repulsive and they grow indefinitelywith decreasing distance between two el-ements (this fact implies that contacts areimpossible).

He published in Latin the poem “De Solisac Lunae Defectibus” in 1769 in London.

Boscovich taught at the University of Paviafrom 1764 to 1768 and at the “Scuole Palatinedi Milano” since 1768. During these years hisactivities concern the school and the BreraObservatory. The Observatory was founded onthe initiative the Jesuits, but Boscovich playeda major role in its development and equipmentwith the best instruments of the time.

Boscovich carried on some measurementsand observations to detect the instrumental er-rors. Boscovich combined different observa-tions to solve this problem and he wrote manymemories about the solution. Schiaparelli saidthat Boscovich tried to avoid the mechanics ob-servations to detect errors and he preferred touse the astronomical observations. This tool isused nowadays. For this reason Boscovich isconsidered a precursor of this technique.

Boscovich designed a water-filled tele-scope with the aim of using it to comparethe corpuscular to the wave theory. A simi-lar instrument was used only in 1871 at theGreenwich Observatory by G. B. Airy.

Boscovich had an argument with LaGrange (the director of the Observatory) andwith the rector of the college of Brera. For thisreason Boscovich stopped working at the BreraObservatory. He decided not to stay there ashonorary director and he stopped teaching atthe “Scuole Palatine”. In 1773, the Jesuit com-pany was suppressed and Boscovich movedfrom Venice to Paris where he became the di-rector of the optical division of the FrenchMarine. He stayed in Paris for ten years; dur-

Crippa et al.: geodetic and cartographic studies 77

Fig. 2. The new map of the Papal State

Fig. 3. Detail of the map in Figure 2.

ing this period he published the solution of thefollowing problems:

• how to determine the comet orbit startingfrom three observations,

• the micrometer• achromatic telescope.

In 1783 Boscovich went to Bassano,Italy and he published “Opera pertinentia adOpticam et Astronomiam” in 1785. This workis focused on optics and astronomy.

In 1785 he stayed in Tuscany for somemonths and then he moved back to Milanthanks to his friends Reggio and Cesaris.

Fig. 4. Front of the book “Geografia storico polit-ica Stato della Chiesa: arricchita di notizie” pub-lished in Venice in 1795.

To summarize the Boscovich’s studies,they are related with:

• optics:– the elimination of the chromatic aber-

ration,– the detection of the spherical aberra-

tion, and

78 Crippa et al.: geodetic and cartographic studies

Fig. 5. Table of names and Table of conversion between different units

– the construction of the optic microme-ter.

• geodesy,• astronomy:

– how to determine the comet orbit,– how to determine the Uranus orbit, and– the detection of the perturbation of the

Jupiter and Saturn orbits.• mathematics:

– he developed a graphic solution tosolve the spherical triangles,

– he developed four differential formulasabout spherical geometry, and

– he studied possible non-euclidean ge-ometry.

2. The Observatory of Brera afterBoscovich

The history of science, technology, thoughts,arts and literature is not the history of isolatedmen, but it that of the desires, the research

and expectations. Big discoveries and inven-tions sometimes occur after determined trials,others succeed by chance, however in a fertileclimate.

Similarly, the school of the BreraObservatory that started with Boscovichcontinues today and consolidates the expec-tations of the scientific community and thetechnical needs of its contemporary society.

Some important contributions from the di-rect successors of Boscovich continue untilthe early 19th century. This is documented inthe “Acta excerpta”, compiled by the archivistGiovanni Antonio Luraschi starting from 1833.To comply with a request from the Austriangovernment, he collected there the copies ofthe records from the Brera Observatories, from1772 to 1860, when Francesco Carlini was di-rector, “Acta excerpta” is part of the historicalarchive of the Brera Observatory.

A chronological index gives precise infor-mation about the material of the archive, as

Crippa et al.: geodetic and cartographic studies 79

Fig. 6. Measurements and their corrections between Rome and Rimini.

completion of the “Acta”. Here are cited onlyAngelo De Cesaris and Francesco Reggio asdirect students, Barnaba Oriani and FrancescoCarlini as direct successors. The structure ofthe school of Brera Observatory was morecomplex and with many more successors.

3. The new map of Papal State

The web-side of the Istituto GeograficoMilitare (IGM) contains a complete and ex-haustive description of the Papal State, writ-ten by fathers Cristoforo Maire and RuggeroBoscovich. This web-site also contains the firstsheet of this map shown in figure 1.

Ruggero Boscovich measured also ageodetic base along the “Via Appia” from“Capo di Bove” to “Frattocchie” near Rome.This work relates to the measure of the merid-ian arc between Rome and Rimini.

The map shown in figure 2 was generatedby Ruggero Boscovich and Cristoforo Maire.Pope Benedictus XIV asked them to measurean arc of meridian between Rome and Rimini.

This work also relates with the problem of theirregular shape of the Earth. The astronomicalobservations were used with the geodetic onesto correct the map of Papal State. This fact im-plies that this map was the first map based onscientific operations. This map was engravedon copper and published in three sheets in 1755at the “Calcografia Pontificia”.

The copy of the Collezione Bianconi (no.233, file B0012901-3) is mounted on canvason a single sheet; the copy of the general in-ventory is on three sheets with colored topog-raphy. This map extends from the mouth of theriver Po to the river Tronto, on the Adriaticsea; to the West it stops at the border of thePapal State; on the side of the Tyrrhenian seait includes the coastal line Porto Ercole-T. d.a.Cerva. The topography is displayed with hatchlines.

The main cities are represented, distin-guishing archbishoprics, bishoprics, cities andlands. The road network is visible. On the topright-hand side, there is a note from the au-thors with some explanations about the gene-

80 Crippa et al.: geodetic and cartographic studies

]

Fig. 7. The hypothetical scheme of the triangulatednetwork between Rome and Rimini

sis of the map. On the left. there is a list withthe main cities, their Latin names, castles andrivers. Under the title there is the dedication toPope Benedictus XIV (detail shown in Fig 3).

Ten different scales are shown, some fromancient Italian cities, others used in the Frenchsystem, others in the English one.

As mentioned before, Boscovich dedicatedthe map to Pope Benedictus XIV. The Popereal name was Prospero Lorenzo Lambertini;he became a cardinal in Bologna and he wasable to compromise with Jansenism.

Figure 4 shows the cover of the book“Geografia storico politica Stato della Chiesa:

Fig. 8. The new map of the Papal State, extractedfrom the book shown in Fig 9

.

arricchita di notizie” published in Venice in1795. This books deals with the historical - po-litical geography of the Papal State, the econ-omy, military power and agriculture and it con-tains many maps.

In this book, a description of the map ofthe Papal State is included. This map was pub-lished in 1755 and it generated a better knowl-edge of the lands. It is also important becauseof its scientific and technological merits.

4. An Attempt to rebuild thetriangulation

The Papal State was displayed in many maps.One of these was generated by Tobia Maierin 1748 with the support of the heirs ofHomann. Another one was generated by theJesuit Cristoforo Maire and it was corrected bythe Jesuit Ruggero Boscovich using astronom-ical observations. They both wanted to com-pare the measurements with the ones elabo-

Crippa et al.: geodetic and cartographic studies 81

Fig. 9. Cover of the book “Voyage Astronomique”

rated by the Academics of the Royal Academyof France and to compare the obtained shapeof the Earth. Across this map, there are the fea-tures measured with its precision.

Figure 5 shows the names of the streetswith the Latin names, castles and rivers. Thesame picture shows a table used to convert dif-ferent measure units and it is contained in thenew Papal State map. The existence of differ-ent measure units was a complex problem inthe 1700s. Only in 1850 the metric system wasadopted in Italy. For this reason the table in fig-ure 5-right is really important.

Tables of logarithms were used to multi-ply and to subdivide. Calculations were per-formed in astronomy, in geodesy and in cartog-raphy. Boscovich and his school were able tojoin mathematical and statistical methods withpractice.

Between 1750 and 1753, Boscovich, to-gether with Cristoforo Marie, measured thelength of the meridian from Rome to Rimini.Marie was a Jesuit brother of the “CollegiumRomanum”. They generated a triangulationnetwork, composed of eleven concatenated tri-angles. The network was dimensioned by ageodetic baseline along the “Via Appia an-tica”, from “Capo di Bove”, not far from themausoleum of Cecilia Metella, to Frattocchie,near Rome. This information was contained

in one of their reports, entitled “De LitterariaExpeditione per Pontificiam Ditionem adDimentiendos Duos Meridiani Gradus etCorrigendam Mappam Geographicam - Iussu,et Auspiciis Pont. Max. Benedicti XIV -Suscepta a Patribus Societ. Jesu ChristophoroMarie et Rogerio Josepho Boscovich XIV.Roma MDCCLV”.

Today we can confirm the excellent mea-surements, with an average error of 1.2” andr.m.s. of 8.9”. The closures do not take intoaccount the spherical effects, also because theclosures by defect prevailed over the straightangles of the 2D triangles. The tables inFigure 6 and Figure 7 show the eleven trian-gles, their vertices, the measured angles andthe adjusted ones thanks to the closures and thelength of one of the three sides of each trian-gle. The modern reiteration with 24 indepen-dent layers generates a r.m.s. equals to 1.8”.This reiteration was not done by Boscovich,but this result confirms that nowadays the gainis on time, not on quality. The identificationof the trigonometric vertices is more difficult,possibly because changes may have occurredto names with time.

For example, a vertex may be located in“Misano Adriatico” near Rimini, because thesea is mentioned. Another vertex in Rome maybe the Saint Peter cathedral, mentioned only as“Th. D. Petri”. The final vertex of this baselineis at “Le Frattocchie”, but the monument is nolonger visible.

It is more probable that the vertex called“Soriano” is located on “Monte Cimino” (1053m a.s.l.) and not at “Soriano del Cimino” (509m a.s.l.). This fact is also supported by thevertices located on the mountains Carpegna,Catria, Pennino, Fionchi and Gennaro. Theyare located respectively at 1418, 1701, 1571,1337 and 1271 m a.s.l.. Figure 7 shows the lo-cations of these points.

To complete this topic, the new map of thePapal State is shown in figure 8. This figurewas extracted from “Voyage Astronomique etGeographique, dans l’Etat ecclesiastique, parles PP. Maire & Boscovich de la Compagniede Jesus, Traduit du Latin, Augmente deNotes d’extraits de degres faites en Italie,en Allemagne, en Hongrie en Amerique.

82 Crippa et al.: geodetic and cartographic studies

Avec une nouvelle Cartes des Etats du Papelevee geometriquement. A Paris MDCCLXX”.Figure 9 shows the cover of the book.

This book was published fifteen years af-ter the first Latin edition and it certifies thepresence of Boscovich in Paris at the time as-tronomers studied Uranus.

This planet was first confused with a star,then it was classified as a new comet and inthe end as a new planet. Boscovich contributedto this European debate and he helped to con-

firm the Copernican theory and to support theGalilean and Newtonian mechanics.

Acknowledgements. A sincere thanks to the as-tronomer Pietro Broglia and to the librarian andarchivist Agnese Mandrino; they both have en-livened the history of the Brera Observatory. A sin-cere thanks to the philosopher Luca Guzzardi, whois a scholar of science philosophy and history of sci-ence and technique.