Oeuvres complètes. Tome VII. Correspondance 1670-1675

[p. 207]

N^o 1900.
H. Oldenburg à Christiaan Huygens.
28 juillet 1672.

La lettre se trouve à Leiden, coll. Huygens.
Elle fait suite au No. 1896. Chr. Huygens y répondit par le No. 1912.

A Londres le 18 juillet 1672.

Monsieur

Vous ayant escrit le 8^me juillet et envoyé la copie de la lettre, de Monsieur Sluse¹⁾ ie ne vous eusse pas si tost importuné de nouveau, si quelques lignes de Monsieur Newton, qui regardent vne partie de la lettre, que vous me fistez l'honeur de m'escrire le 1. juillet, ne m'y eussent obligé. Je vous les donneray dans la mesme langue, que ie les ay receu. Il dit donc,

I am glad to find by y^e abstract of Monsieur Hugenius his letter, which you transmitted to me, that he who hath done so much in Dioptricks hath been pleased to vndertake the improvement of Telescopes by Reflexions also; though without y^e desired success. I hope, y^e event of his next essay, if he shall think fit to attempt any thing further, will prove more happy by a litle altering y^e manner of his proceding. As for me, I know not, whether I shall make any further tryals myself, being obliged to prosecute some other subjects.

As to y^e Theory of Light and Colors, I am apt to belieue, that some of the Experiments may seem obscure by reason of y^e brevity, where with I writ y^m, which should haue been described more largely, and explained with schemes, if they had been intended for the publick. But I see not, why the Aberration of a Telescope should be more than about 1/50 of y^e Glasses aperture. For, suppose DF be



y^e Lens, CD and EF two lines parallel to its Axis, in which or indesinitely near to which, all variety of difforme rays are successively incident on two opposite parts of its Perimeter: And of those rays let DH and FG be the most refracted, and DG and FH y^e least refracted, intersecting y^e former in G and H. Draw GH, and produce it both ways, till at M and N it occur with CD and EF, also produced. Now, since by my Principles y^e difference of Refraction of y^e most difforme rayes is about y^e 24^th or 25^th part of their whole refraction, y^e Angle GDH will be about a 25^th part of y^e Angle

1) Voir la Lettre N^o. 1897.

[p. 208]

MDH, and consequently the subtense GH (which is y^e diameter of y^e least space, in to which y^e refracted rays converge) will be about a 25^th part of y^e subtense MH, and therefore a 49^th part of y^e whole line MN, y^e diameter of y^e Lens; or, in round numbers, about a fiftieth part, as I asserted.’

Apres auoir transcrit cecy, ie n'y ay rien à adjouster, si non que ie fais imprimer a present dans mon journal la plus propre methode descrite de Monsieur Newton pour establir sa doctrine de la Lumiere et des Conleurs³⁾. Quand il sera achevé d'imprimer, ie vous l'envoieray des aussi tost, come

Monsieur

Vostre tres humble et tresobeissant serviteur Oldenburg.

A Monsieur

Christian Hugens de Zulechem, a la bibliotheque du Roy à

Paris.

3) A Serie's of Quere's propounded by Mr. Isaac Newton, to be determined by Experiments, positively and directly concluding his new Theory of Light and Colours; and here recommended to the Industry of Lovers of Experimental Philosophy, as they were generously imparted to the Publisher in a Letter of the said Mr. Newtons of July 8. 1872. Phil. Trans. N^o. 85, du 15 juillet 1672 [V. st.].