II. - Schloss Schwetzingen

II.
72
Fig. 8: Anniversary of the
transit of Venus in 2004.
II. Schwetzingen – A Prince Elector’s Eighteenth-Century Summer Residence
horologist, André Le Paute Mayer bought an
upright clock with a second-beating pendulum,
which cost 12 louis d‘or, with the intention
of using it for his astrological observations.
The quadrant has been preserved; the clock’s
whereabouts are unknown. It was fi rst put up
in one of the rooms at Schwetzingen Palace,
that was briefl y used as an astronomy cabinet,
but went missing in the 20th century.
The quadrant was the fi rst instrument usable
for both astronomy and geodesy, that was
acquired by the small astronomy lab in
Schwetzingen. It was used for land surveying
(triangulation) and for determining the
altitude of stars.
Mayer’s aim was to determine a meridian
and make a full survey of the Palatinate. 19 In
1760, he ordered a semicircumferentor with
a compass and two telescopes (graphometer)
from Canivet, and in 1761, he ordered a copy
of the French unit of measure, a toise (c.1,949
m). With the quadrant he now had the
complete, state-of-the-art equipment for his
planned survey.
19 GLA 213/No. 3540 Mannheim Stadt. Acta die neue Sternwarte
betreff. Vol. I, Denkschrift Mayers zum Neubau einer Sternwarte
in Mannheim vom 31. 12. 1771, p. 171.
The Transit of Venus, 1761
Astronomers set great store by the transit of
Venus across the sun on 6th June 1761. From
the observations made at the time, and from
measuring the angles of Venus entering and
exiting the sun’s disk, they hoped to gain
new evidence of the derivation of the solar
parallax, and thus of the distance from the
earth to the sun. Measuring was to take place
in numerous places all over the globe; almost
200 astronomers were at their posts at more
than 120 observation sites. In Europe the
transit began early in the morning.
At Schwetzingen, a wooden platform was
built in the garden in front of the orangery,
and on this Mayer arranged his observation
instruments.
At this point the question arises about which
“orangery” was being referred to. Today’s
orangery, with its open square was built by
Nicolas de Pigage in 1761-63, and its garden
with the bridges is even later (1764). 20 It must
be assumed that the documents refer to the
north and south quarter-circle pavilions, built
after the Old Orangery of 1755 had been
pulled down and called “the new orangery
buildings” in the plans. 21 Mayer’s observation
platform would have been on the cleared site
of the former Old Orangery, more or less on
the park’s central axis and west of the Arion
fountain. The site was suffi ciently distant
from the palace, which was off to the east, to
permit an unobstructed view.
The platform would have been a simple raised
wooden construction with a fl oor of solid
planks, spacious enough for the astronomer,
his assistant, and his equipment. From there
the instruments were pointed at the rising
sun. The transit had started well before
sunrise, and in Schwetzingen it was over
around 8.35 a.m.
It had been hoped that the measurements
taken all over the world, in what was in effect
20 Hubert Wolfgang Wertz, “Die Schwetzinger Orangerien”, in:
Der Süden im Norden. Orangerien – ein fürstliches Vergnügen.
(Ed. Oberfi nanzdirektion Karlsruhe Staatliche Schlösser
und Gärten und Arbeitskreis Orangerien in Deutschland e. V.),
Regensburg 1999, p. 67.
21 Wertz 1999, fi g. on p. 58, plan of expropriations between 1748
and 1762.