Sir Is a ac Newton’s Book III.

might be extracted from our author, give abundant proof of theprelent point. I fhall only lubjoin one more: thefe tranfpa-rent plates tranfmit through them all the light they do not re-fled:; fo that when looked through they exhibit thofe colours,which relult from the depriving white light of the colour re-fleded. This may commodioufly be tryed by the glaffes fooften mentioned ; which if looked through exhibit colouredrings as by reflected light, but in a contrary order; for the mid-dle Ipot, which in the other view appears black for wantof refleded light, now looks perfectly white, oppoflte tothe blue circle; next without this fpot the light appearstinged with a yellowifh red; where the white circle ap-peared before, it now leems dark ; and fo of the reft a .Now in the fame manner, the light tranfmitted through fo-liated gold into a darkened room appears greenilh by thelofs of the yellow light, which gold refleds.

1^. Hence it follows, that the colours of bodiesgive a very probable ground for making conjedure concerningthe magnitude of their conftituent particles b . My reafon forcalling it a conjedure is, its being difficult to fix certainly theorder of any colour. The green of vegetables our au-thor judges to be of the third order, partly becaufe of the in-tenfenefs of their colour; and partly from the changes theyfuffer when they wither, turning at firft into a greenifh ormore perfed yellow, and afterwards fome of them to an o~range or red; which changes feern to be effeded from theirringing particles growing denfer by the exhalation of their

» Ob'erv. 9, b Ibid prop. 7.

2

moifture