Lenses and Waves

1690 - TRAITÉ DE LA LUMIÈRE 215
plan, and I do not know when I would have been able to put this to order, being often
diverted either by things to do or by some new study. ” 2
It was true, many things had distracted him since his ‘Eureka’s’. In the
summer of 1678, Hartsoeker and Leeuwenhoek had kindled his interest in
microscopes and microscopical observation. He devised several
Leeuwenhoek-style simple microscopes himself and made some technical
improvements and additions. 3 In 1680, he published a design for a telescopeenhanced
level, followed by disputes which lasted for years. 4 Around the
same time he studied the properties and nature of magnetism. Back in
Holland, Huygens designed his planetarium and continued working on his
pendulum clock and its application at sea. With Constantijn he
recommenced the grinding of lenses and manufacture of telescopes, earning
fame for their skills and creating demand for their products. 5 They built a
grinding lathe and Huygens published the description of an aerial telescope
of his design, Astroscopia Compendaria (1684). Around the same time the
brothers were also discussing a treatise on the grinding of lenses. 6 So, even if
the list is confined to optical matters there was enough to divert his attention
from his treatise in dioptrics. Moreover, Huygens somewhat lost interest in
his theory, witness his response to Leibniz’ inquiries after his wave theory.
During the 1680s Leibniz repeatedly asked him his opinion on the nature of
light and refraction, but Huygens proved rather reluctant to discuss the
details of his wave theory. He replied Leibniz’ questions were often much
later and when he did he was rather succinct and shallow. 7
The delay was not only effected because other things caught Huygens’
eye. His indecisiveness as regards the final format of his optics, to which he
alluded in the first sentences quoted above, also played a part; a substantial
part in my view. Although the preface does not say so, Traité de la Lumière
had been intended as part of a treatise on dioptrics, rather than an
accompanying discours. Until Traité de la Lumière went into print, Huygens
had maintained his original plan of a ‘Dioptrique’ of which his theory of light
was an integral part. When he presented it to the Académie, he had upgraded
his wave theory to form a separate part, but still the ‘first part’ of his
‘Dioptrique’. Now, in 1690, Huygens mentioned ‘Dioptrique’ as a separate
2
Traité, ‘Preface’, [1]. “On pourra demander pourquoy j’ay tant tardé à mettre au jour cet Ouvrage. La
raison est que je l’avois escrit assez negligement en la Langue où on le voit, avec intention de le traduire en
Latin, faisant ainsi pour avoir plus d’attention aux choses. Apres quoy je me proposois de le donner
ensemble avec un autre Traité de Dioptrique, ou j’explique les effets des Telescopes, & ce qui apartient de
plus à cette Science. Mais le plaisir de la nouveauté ayant cessé, j’ay differé de temps à autre d’executer ce
dessein, & je ne sçay pas quand j’aurois encore pû en venir à bout, estant souvent diverti, ou par des
affaires, ou par quelque nouvelle étude.”
3
For example: OC8, 112-113. For details on his observations: Fournier, “Huygens’ observations”.
4
OC8, 263-266; 273-276, and further.
5
The quality and distribution of their lenses is recorded in Van Helden & van Gent, The Huygenscollection
and Van Helden and van Gent, “Lens production”.
6
For example: OC8, 432-435; OC9, 8; 25.
7
See OC8, 244-245; 250-251; 256-257; 267; OC9, 259.