Letter from Henry Oldenburg to Newton, dated 2 July 1672

London july 2. 72.

Sir,

I doubt not but you haue receiued both my last letters to you, of jun. 20 and 25; of which one was sent to Cambridge, because I then know nothing of your excursion into Lincolnshire; the other to Woolstrope in Coulsterworth parish as you directed in yours of june 19^th. I shall not repeat the contents of them, but acquaint you rather with some particulars, I receiued lately from Monsieur Hugenius wherein you are somewhat concerned. As that learned Gentleman hath a particular esteem of you, so he wisheth very much, that your Reflecting Telescope, and also your new doctrine of light and Colors might be so improved and made out, as to silence all contradicti{o}n{s}. I shall giue you, what he saith to me of both in a late letter of july 1. st. n, in his own words:

1. Concerning the Telescope;

Pour ce qui est des Lunettes de Monsieur Newton ie souhaite fort, qu'il voulût luymesme; qui en est l'inventeur, tascher de les perfectionner, et d'en faire de plus grand volume que celles de 7. ou 8 pouces. Ie vous ay mandé des le commencement que i'en espereis de grands effets, pourvû qu'on trouvast dela matiere qui fut capable d'un beau poli come celuy du verre, et que l'on pût donnez ce poli sans alterer la figure des miroirs. I'ay encor peur que ce ne soit lá le grand obstacle; par ce que <16v> dans les essais, que i'ay fait dernierement i'ay trouvé cete matiere de fonte incomparable plus molle que celle du vitre: ce qui paroit en ce que le dernier poli des miroirs concaues, que ie n'ay sceu donner qu'en me servant de quelque chose de mol, come sont le linge et le cuir, a gasté visiblement la perfection sela figure spherique, qui faisoit desia auparavant vne reflexion tres reguliere, mais obscure. I'auois donné la figure et le douci en frottant deux miroirs de mesme matiere l'un sur l'autre, et puis i'y appliquay du linge entre deux au{ec} dela pottee d'esta{in}: Et cependant ie trouvay, que cete maniere de polir gastoit de plus en plus la parfaite sphericité. Vous n'obligerez (saith he to me further) de me mandez oú en est Monsieur Newton luy mesme. Mon miroir estoi{x} de 12 pieds de foier, mais seulement de 4 pomes de diametre.

2. Touching your doctrine of Light, he saith; j'avv{uë}, que la nouuelle Theorie des Couleurs, advancé par M. Newton, me paroit iusques iay tres-vraysemblable, et L'Experimentum crucis (si ie l'enterds bien, car il est escrit on peu obscurement) la confirme beaucoup.

Mais sur ce qu'il dit de l'aberration des rayons à travers des verres convexes, ie ne suis pas de son avis. Car ie trouvay en lisant son escrit, que cete aberration suivant son principe devroit estre double de ce <17r> qu'il l'a fait, s{a}voir $\frac{1}{25}$ de l'ouverture du verre; à quois pourtant l'experience seuble repugner: De sorte que peut estre cete aberration n'est pas tousiours proportionelle aux angles d'inclinaison des rayons.

So far He, which I could not forbear to impart to you, presuming you would not be displeased to see, what so famous a person, as M. Hugens, Iudgeth of your discoveries and sentiments. I intend, God permitting, to write to him by the next mundays post; and if you haue any thing to returne to him, I shall be glad to receiue it, and to convey it to him. you may write what you haue to say to him vpon this occasion, either in Latin, or English, he being a great master of the English tongue; though, I think, such subjects as these are best managed among the Learned in Latin.

Pardon this prolixity to

Sir

your faithful servant

H. Oldenburg.

if M^r Hook make any return to your answer (as he is like to doe) I doubt not but I shall haue the liberty of imparting it to you.

I pray, Sir, order your Carrier to send to my house by the next; for I haue something for you, which I cannot conveniently send by the post.

<17v>

To his much honord friend M^r Isaac Newton Professor of the Mathematicks in the University of Cambridge, at his Chamber in Trinity Colledge.

Cambridge