Letter to Henry Oldenburg, 19 March 1671 Isaac Newton c. 514 words The Newton Project Falmer 2014 Newton Project, University of Sussex

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 19 March 1671, in English, c. 526 words, 2 pp. 2 pp.

Published in H.W. Turnbull (ed), The Correspondence of Isaac Newton, vol. 1 (Cambridge: 1959), p. 121

Letter to Henry Oldenburg, 16 March 1671 [EL/N1/35]

in English

 EL/N1/36, Royal Society Library, London, UK UKLondonRoyal Society Library EL/N1/36 19 March 1671 England English Holograph Unknown Cataloguer (1) Unknown Cataloguer (2) Henry Oldenburg Unknown Hand (3) ScienceOpticsCorrespondence Transcription by Daniele Cassisa Code audited by Michael Hawkins
36Newton 236Trans 1672

Mr Newtons Letter to Mr Oldenb. containing some Advertisements about his Reflecting Telescope.

Read Mar: 21: 71

Enter'd LB. 5. 364.

SrSir

In my last letter I gave you occasion to suspect that the instrumntinstrument wchwhich I sent you is in some respect or other indisposed, or that the metalls are tarnished. And by yoryour letter March 16 I am fully confirmed in that opinion. For whilest I had it, it magnified represented the Moon in some parts of it as distinctly as other Telescopes usually doe wchwhich magnify as much as that. Yet I very well know that that instrument hath its imperfections both in the composition of the metall & in its being badly cast as you may perceive by a scabrous place nereneare the middle of the middetale of the metallon yethe polished side, & also in the figurede of that metall neare that scabrous place. And in all those respects that instrument is capable of further improvement.

You seem to intimate that the proportion of 38 to 1 holds holds onely for its magnifying objects at small distances. But if for such distances suppose 500 foot it magnify at that rate, by the rules of opticks it must for the greatest distance imaginable magnify more then 3734 to 1 wchwhich is so insensible a diminishing that I it may be even then put as 38 to 1.

I told you that here is another instrument made like the former wchwhich doth very well. Yesterday I compared it wthwith a six foot Telescope & found it not onely to magnify more but also more distinctly. And to day I found that at a hundred foot distance I could reade in one of the Philosophicall Transactions placed in the sun's light at a hundred foot distance, & that at a hundred & twenty foot distance I could discern some of the words. When I made this tryall its aperture (defined next the eye) was equalentequivalent to more then an inch and a third part of the object metall. This I thought good to inform you of because it may be of some use to those that shall endeavour any thing in reflectxions. For hereby they will in some measure be enabled to judg of the goodness of their instruments. &And for this end you may annex these observations made wthwith this last instrument, to the description of it in the Transactions of this Month. But my answer to Mr Hooks observations will not be ready for then, because I intend to annex to that answer some further explications of the Theory, wchwhich I shall not have leisure to do this week or fourtnight. SrSir I am in hast YorYour Faithfull servant. I. Newton March 19th. 1671. Envelope text written upside down on page These For Henry Oldenburg Esqꝫ. at his house neare the middle of the old Pall-mail in Westminster London 2 Rec.Received March. 20. 71. Answ.Answered March. 23. comm. yethe Comet and sub cap Cygni from Hevel. i.e. if yethe bentlens axis were direct were accounted streight,