London Sept. 24. 1672.

Sir,

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

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

'Tis added, ytthat yesamethesame person was going to make another of a bigger size after the conceit of M. Cassegrain; though he does not agree wthwith yesdthesaid Cassegrain, to make convexe ytthat litle glass, wchwhich one looks into by means of yethe Eye-glass; and belieues wthallwithall (NB) that yethe this French man only thought vpon ytthat contrivance, to disguise as much as was possible his pretended new Invention (wchwhich, by yethe by) is none of his,) wchwhich he endeavour'd to make appear anterior to Mr Newtons most noble one.

So far my Correspondent of Florence; by wchwhich you see, that yryour productions are spred further than perhaps you are aware of: wchwhich, he thinks, should increase your rigour to prosecute and advance them to the vtmost, as well for yryour owne as the Nations honor.

And this, I hope, will prove a motive to you to perfect, ytthat is, to render indubitable to all, yryour new Theory of Light, and to take it again into Consideraonconsideration, as soon as conveniently you can, particularly by finishing and what by yryour last appears you haue now laid aside; I mean by drawing vp a series of ExperimtsExperiments tending to evince each part of ytthat Theory.

Having done wthwith this, I am, before I conclude, to desire you to let me know, if wthoutwithout inconvenience you can, by yethe first, whether a young Chymist, that hath lived many years wthwith 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 [29] for making wthwith 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, forthwthforthwith to visit yryour University, and to endeavour soto approve himself, as may in some measure answer exspectation, and the recommends of

Sir

yryour humble and faithful servt:servant

Oldenburg.

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

Ce que vous auez mis de MonsrMonsieur 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, que 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 in his owne words, not doubting but you are master of yethe French tongue.

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

Cambrige.

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