<32r>

London Iune 7. 73.

Sir,

Where I find you concern'd, I cannot omit giuing you notice of it, and 'tis vpon that score, that, though I wrote to you but the other day, when I sent you Monsieur Hugens's book de Motu Pendulorum (which was on Thursday last by your carrier,) I make so much haste of writing to you again, that so I may acquaint you with some particulars, since come to my hands in a letter from the same M. Hugens, as follows in his owne words;

Paris, june 10. 1673. st. n.

Pour ce qui est des solutions de Monsieur Newton aux doutes que i'auois proposez touchant sa theorie des Couleurs, il y auroit dequoy y respondre et former encore de nouuelles difficultez; mais voyant qu'il soustient sa doctrine auec quelque chaleur, ie ne veux pas disputer. Cependant que veut dire, ie vous prie, qu'il avance, que quand mesme ie luy aurois montré que le blanc se peut composer de deux seules couleurs primitives, ie n'en pourrois pourtant rien conclurre contre luy, et cependant. il a dit pag. 3083. des Transactions, que pour composer le blanc, toutes les couleurs primitives sont necessaires.

Quant à la maniere dont il concilie l'effet des verres convexes à assembler si bien les rayons, <32v> auec ce qu'il establit touchant la differente refrangibilité; I'en suis satisfait: mais aussi doit il avouër, que cette aberration des rayons ne nuit donc pas tant aux verres, qu'il semble auoir voulu faire à croire, quand il a proposé les miroirs concaves comme la seule esperance de perfectioner les Telescopes. Son Invention assurement estoit tres-belle, mais, à ce que i'ay pû conoitre par l'experience, le defaut dela matiere la rend presque aussi impossible d'executer, que la difficulté dela forme repugne aux Hyperboles de M. des Cartes: de sorte qu'à mon avis il en faudra deneurer à nos verres spheriques, auxquels nous auons desia tant d'obligation, et qui peuvent recevoir encor plus grande perfection tant par l'augmentation dela longueur des lunettes, que par la correction dela matiere du verre mesme.

So far He: which I thought fit to hasten to you, that you might, if you pleas'd, take notice of it to him, when you send him your thanks for his book.

The words of your Answer of April. 3. 73, which he thinks doe clash with those in the Transactions, are these;

if therefore, M. Hugens would conclude any thing, he must show, how white may be produced out of two vncompoundded colors; which when he hath done, I will further tell him, why he can conclude nothing from that?

This, I suppose, was not said by you in contradiction to that paragraph of p. 3083. in Transactions, but with refe <33r> rence to the main import of your Theory, viz. that that would not be overthrown by it, though perhaps that part concerning the composition of whiteness should fall.

But I leaue it to yourself, to satisfy M. Hugens, exspecting your notice of having receiued this from

Sir

your humble and faithful servant

Oldenburg

<33v>

To his honored Friend Mr Isaac Newton professor of the mathematiques, at his Chamber in Trinity-Colledge in

Cambridge

2

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Professor Rob Iliffe
Director, AHRC Newton Papers Project

Scott Mandelbrote,
Fellow & Perne librarian, Peterhouse, Cambridge

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