<28r>

London Sept. 24. 1672.

Sir,

I had no sooner receiued ye favour of yr answer to my last, but the forrain post brought me a pacquet out of italy from Signor Magalotti, Secretary to ye Florentin Academy, and \from/ another gentleman, both residing at Florence; giving me notice of some particulars, wherein you being concern'd, I cannot omit to|h|ere to transcribe ym for you. They are to this purpose;

That one Signr Pietro Salvetti, havin one of ye Great Dukes Musitians, having applied himself to ye study of the mathematicks, and particularly to yt of ye Proportions of Harmony, as relating to his Profession of musick, began to delight himself in Opticks; and not being content wth ye Theory, attempted to putt it in practice by making Telescopes and microscopes in imitaon of those of Campani and Divini: And yt he lately shew'd one of his Microscopes to ye G. Duke, wch was Iudged by all much better than any of ye best, his Highnes had; and yt yesame same day he likewise shew'd his litle Highnes a litle Prospective Glass wch he made according to Mr Newton's new invention, and although this was ye first, and not above half a foot long, it had thesame effect as one of ye common way of two foot.

'Tis added, yt yesame person {illeg}|w|as going to make another of a bigger size after the conceit of M. Cassegrain; though he <28v> does not agree wth yesd Cassegrain, to make convexe yt litle glass, wch one looks into by means of ye Eye-glass; and belieues \wthall/ (NB) that ye this French man only thought vpon yt contrivance, to disguise as much as was possible his pretended new Invention (wch, by ye by) is none of his,) wch he endeavour'd to make appear anterior to Mr Newtons most noble one.

So far my Correspondent of Florence; by wch you see, that yr productions are spred further than perhaps you are aware of: wch, {illeg}|h|e thinks, should increase your rigour to prosecute and advance them to the vtmost, as well for yr owne as the Nations honor.

And this, I hope, will prove a motive to you to perfect, yt is, to render indubitable \to all,/ yr new Theory of Light, and to take it again into Consideraon, as soon as conveniently you can, particularly by finishing and w{h}{a}t by yr last appears you haue now laid aside; I mean by drawing vp a series of Experimts tending to evince each part of yt Theory.

Having done wth this, I am, before I conclude, to desire you to let me know, if wthout inconvenience you can, by ye first, whether a young Chymist, that hath lived many years wth Mr Boyle, and attained to good skill in that Art, as I am very credibly inform'd, \he hath, I mean (call'd Mr Thom. Huyck)/ may, be repairing to Cambridge and there offring his service to ingenious and curious persons <29r> for making wth you a good course of Chymistry, find acceptance, and a competent reward for his skill and pains? If you think he may, he intends, God willing, forthwth to visit yr University, and to endeavour soto approve himself, as may in some measure answer exspectation, and the recommends of

Sir

yr humble and faithful servt:

Oldenburg.

After I had written this, there comes to my hand a letter from Monsr Hugenius, wherein are these laws touching yr doctrine of Colors, viz.

Ce que vous auez mis de Monsr Newton dans vn de vos dernieres Transactions, confirme encor beaucoup sa doctrine des Couleurs. Toutefois la chose pourroit bien estre autrement; et il me semble qu'il se doit contenter, que ce qu'il a advancé passe pour vne hypothese fort vray-semblable. de plus, quand il seroit vray, qu{e} les rayons de lumiere, dés leur origine fussent les vns rouges, les autre bleus etꝫ. il resteroit encore la grande difficulté d'expliquer par la physique mechanique, en quoy consiste cete diversité de couleurs.

I thought fit to giue you this {illeg} in his owne words, not doubting but you are master of ye French tongue.

<29v>

To his honor'd friend Mr Isaac Newton, Professor of the Mathematicks in the University of Cambridge, at his Chamber in Trinity Colledge

Cambrige.

2

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