Christiaan Huygens – A family affair - Proeven van Vroeger

the Zulichems, Father and Son: all foure, inquisitive after you.” 374 The letter bespeaks a respect
for father Huygens that he and his son had probably aimed for. It is unclear whether father
Huygens attended more meetings with experimental philosophers during his stay in London;
Robert Hooke did not mention him in his letters to Boyle in which he indicated that Christiaan
managed to show him the phenomenon of anomalous suspension. 375
The most substantial role for Constantijn Sr. and Christiaan’s brothers in the showing
of Christiaan’s instruments was in Parisian meetings during the period 1661-1665 where
telescopes were compared and phenomena in the skies observed. Though effectively the
“reign” of the Huygens-telescope may have been over with the coming of the Campani-
telescope in 1662, 376 the Paris- and London-groups could not compare the two until
Constantijn Sr. managed to get a Campani-telescope in 1664, and the Huygens telescope was
at the center of attention until at least the beginning of 1665. It seems that all of the Huygens
carried their own telescopes – Lodewijk received Constantijn Sr.’s old version when the latter
wished for a better one 377 – not just to stare at the heavens at night, but also to show the
instrument to members of the Montmor-Académie and other courtiers. Constantijn Sr. showed
Christiaan’s telescope to the French King at the Louvre somewhere between November 1661
and March 1662 – an event where the instrument (adjusted to a size worthy for the French
ruler) was “confiscated” by the King, as Christiaan had expected. 378 Later, as both Constantijn
Sr. and Christiaan’s brother Lodewijk frequented the Montmor-group, Lodewijk received a lot
of technical information on the telescope and was used as an intermediary to disclose the secret
374 Oldenburg continued: “They were entertained first with some Experiments, which the bearer hereof
will give you a good account off: and afterwards with good store of occasionall observations, discoursed
of promiscuously, pro re nata; which the strangers (as well as our company) seemed to be much more
pleased with, than with set and formall discourses.” In: HUYGENS, C. (1888) OC., Vol. IV, No. 1122
(Jun. 20, 1663)
375 Ibid., Vol. IV, No. 1136 (July 20, 1663); No. 1138 (July, 1663)
376 RIGHINI BONELLI, M. L. & VAN HELDEN, A. (1981) Divini and Campani: A Forgotten
Chapter in the History of the Accademia del Cimento. Annali Dell'Istituto E Museo Di Storia Della Scienza
Di Firenze, 1-176., p43
377 Constantijn Jr., himself an experienced grinder and telescope-maker, carried his own. His father
received a new telescope around October 1662, leaving the older, smaller one for his other son
Lodewijk. HUYGENS, C. (1888) OC., Vol. IV, No. 1058 (Sep. 7, 1662), No. 1066 (Sep. 28, 1662)
378 Ibid., Vol. III, No. 920 (Nov. 23, 1661): “La Lunette a ce qui me semble court grande risque, s’il faut
que Sire Louis la voie; car il sera tenu de dire qu’elle est fort bonne et mon Pere qu’elle est a Sa Majesté
si elle l’agree.” Vol. IV, No. 996 (Mar. 15, 1662): “Je prevoiois bien que ma lunette seroit confisquée si
elle venoit au Louvre”. Christiaan was prepared to adjust his telescope (lunettes) according to “la
grandeur” of the King: Vol. IV, No. 999 (29 March, 1662).
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