202
12.2 Geodetic Baselines at the Via Appia Antica (1751
and 1854–1855)
In 1751, at the instruction of Pope Benedict XIV (1675–1758), the Jesuit priests
Roger Boscovich (1711–1789) and Christopher Maire (1697–1767) measured a
geodetic baseline along the Via Appia Antica for the calculation of the Rome-Rimini
meridian arc (Maire and Boscovich 1755). The baseline on the Via Appia Antica
that Boscovich established began in the middle of the inscription (titulus) of the
mausoleum in Cecilia Metella (Endpoint α) and ended at a simple stone buried in an
old tomb at Frattocchie (in the municipality of Marino) called Endpoint β.
French engineers who reviewed this work at the beginning of the nineteenth
century placed a marble plaque on Cecilia Metella, right under the titulus, to indicate
Endpoint α (Filippi and Aebischer 2011):
[LES] OFFI. DU CORPS IMPÉ.
DES INGÉ. GÉOG. FRAN.
ONT RETROUVÉ ET RETAB.
CE TERM. OCCI. DE LA BASE
MESUR. EN 1751. PAR LES
P.P. MAIRE ET BOSCOVICH
POUR LA DÉTERMIN. D’UN
DEGRÉ DU MERID. DE
ROME.
MDCCCIX. AN. V. DU REG.
DE NAPOLEON EMPER.
DES FRAN. R. D’ITA. ET
PROTEC. DE LA CONFÉD.
DU RHIN, ET DUC DE
FELTRE ETANT MINISTRE
DE LA GUERRE ET LE
COMTE DE MIOLLIS
GOUVERNEUR DES
ETATS ROMAI.
Over time, however, Endpoint β was lost, and French engineers were unable to
recover it. Instead, they found a buried parallelepiped granite stone with an engraved
cross and, assuming it to be Endpoint β, raised a pyramid or pillar there (probably
with a commemorative inscription, though this too was soon lost). Using this stone,
the French measured the length of the baseline with a series of triangulations and
claimed that Boscovich had been in error by 10 m (Coraboeuf 1853). Such an error
was considered excessive, so much so that the astronomers of the Roman College
wanted to verify it starting from the small baseline measured immediately outside
the Angelica door (Ricchebach 1846; Calandrelli 1855?-1858?). The result was that
these baselines agreed well, so they concluded that the stone found at Frattocchie by
the French was not the actual endpoint of the Boscovich baseline.
The occasion for a new measurement in the mid-nineteenth century was due to
the excavations by Luigi Canina (1795–1856) between 1850 and 1853, which
brought to light the route and the monuments of the Via Appia Antica from Mile IV
T. Aebischer
12.2 Geodetic Baselines at the Via Appia Antica (1751
and 1854–1855)
In 1751, at the instruction of Pope Benedict XIV (1675–1758), the Jesuit priests
Roger Boscovich (1711–1789) and Christopher Maire (1697–1767) measured a
geodetic baseline along the Via Appia Antica for the calculation of the Rome-Rimini
meridian arc (Maire and Boscovich 1755). The baseline on the Via Appia Antica
that Boscovich established began in the middle of the inscription (titulus) of the
mausoleum in Cecilia Metella (Endpoint α) and ended at a simple stone buried in an
old tomb at Frattocchie (in the municipality of Marino) called Endpoint β.
French engineers who reviewed this work at the beginning of the nineteenth
century placed a marble plaque on Cecilia Metella, right under the titulus, to indicate
Endpoint α (Filippi and Aebischer 2011):
[LES] OFFI. DU CORPS IMPÉ.
DES INGÉ. GÉOG. FRAN.
ONT RETROUVÉ ET RETAB.
CE TERM. OCCI. DE LA BASE
MESUR. EN 1751. PAR LES
P.P. MAIRE ET BOSCOVICH
POUR LA DÉTERMIN. D’UN
DEGRÉ DU MERID. DE
ROME.
MDCCCIX. AN. V. DU REG.
DE NAPOLEON EMPER.
DES FRAN. R. D’ITA. ET
PROTEC. DE LA CONFÉD.
DU RHIN, ET DUC DE
FELTRE ETANT MINISTRE
DE LA GUERRE ET LE
COMTE DE MIOLLIS
GOUVERNEUR DES
ETATS ROMAI.
Over time, however, Endpoint β was lost, and French engineers were unable to
recover it. Instead, they found a buried parallelepiped granite stone with an engraved
cross and, assuming it to be Endpoint β, raised a pyramid or pillar there (probably
with a commemorative inscription, though this too was soon lost). Using this stone,
the French measured the length of the baseline with a series of triangulations and
claimed that Boscovich had been in error by 10 m (Coraboeuf 1853). Such an error
was considered excessive, so much so that the astronomers of the Roman College
wanted to verify it starting from the small baseline measured immediately outside
the Angelica door (Ricchebach 1846; Calandrelli 1855?-1858?). The result was that
these baselines agreed well, so they concluded that the stone found at Frattocchie by
the French was not the actual endpoint of the Boscovich baseline.
The occasion for a new measurement in the mid-nineteenth century was due to
the excavations by Luigi Canina (1795–1856) between 1850 and 1853, which
brought to light the route and the monuments of the Via Appia Antica from Mile IV
T. Aebischer