A Letter of Mr. Isaac Newton, Professor of the Mathematicks in the University of Cambridge; Containing His New Theory about Light and Colors: Sent by the Author to the Publisher from Cambridge, Febr. 6. 1671/72; In Order to be Communicated to the R. Society

I. Newton
1671 Philosophical Transactions of the Royal Society of London  
1 Ffiin order to be communicated to the R. .Society* SIR, perform my Iat£ promife to you, I (hall without further J_ ceremony acquaint you, that in the beginning of the Year 1666 (at which time I applyed my felf to the grinding o f Optick igures than S p h e r i c a l, ) I procured me a Triangu lar glafs-Prifme, to try therewith the celebrated Phenomena o f Gggg Colours, ( ) * Colours. And in thereto having darkened my chamber,and ma4e a fm dl hole in tay .window* In tits, to let in a
more » ... let in a convenient quantity of the Suns light, I placed my.Prifme at his entrance,that it might be thereby refradedjto the o p p o fe wall. It was at firft "t0 view the'vivid' and intenfe co lours produced thereby 5 but after a while applying my fdftocpnfider them more circumfpedtly, 1 became furprifed to fee them in a n oblong form $ which, according to the received laws o f Refra, $ion, I expected fliould have been ♦, They were terminated at the (ides with (freight lines, but at-the ends, the decay of light was fo gradual, that it was difficult to de termine juftly, what was their figure i yet they feemeA/^wwculau Comparing the length of thispoloured S p e U rw ith its Itfound itabopt five times greater $ a disproportion fo extrava* gant, that it excited me to a more then ordinary curiofity o f ex amining, from whence it might proceeds I could fcarce think, that the various T h i c k n e f so f the glafs, or the termination with fha dow or darknefs, could have any Influence on light to produce fuchan effect $ yet l thought it not amifs, firft to examine thofe circumftances, andfo tryed, what would happen by tranfmitting light through parts of the glafs of divers thickneffes, .or through holes in the window of divers bigneffes, or by felting the Prifme without fo, that the light might pals through it, and be refra&ed before it was terminated by the hole : But I found none o f thofe oircumftances material The fafcion of the colours was in all thefe cafes the fame. Then IdufpctSed, whether byany unevenmfs'xw the glafs, orother contingent irregularity, thefe colocrs might be thus dilated. And to try! this, I tdok another Prifme like the former, and fo placed it, that the light, pafling through them both, might be re* fradted contrary ways, and fo by the latter returned into that courfe,from which the former had diverted it. For, by this means I thought, the regular effects of the firft Prifme would be def by the fecond Prifme, but the irregular ones more augmented^ by the multiplicity of refra&ons*. The event was, that the light, which by the firft.Prifme was diffufed into^^an
doi:10.1098/rstl.1671.0072 fatcat:jgf746fldvcn7hg5uicdbxtj54