theprerent fcituation and order of Colours, arifeth not from 
anyintrinfecal property of refrangibility (as maintained by 
WMevpton) but from contingent and extrinfecal circumftances 
of neighbouring ob jefts. For accordingly as the body be- 
hind the Paper-circle was more or lefs illuminated than the 
Circle it felf, all the feverai Colours changed their fcitua- 
tion. 
8. Tl^e next Experiment was made in order to Mr. ISfewtoffs 
doflrine of primary Colours, as Prof,^. Having covered the 
Hole in the Window-fliucs with a thin fl'ce of Ivory ^ the tranf- 
mitted li^ht appeared yellow ; but upon adding three, four, 
and more^ices, ir became red. Whence it feems to follow, that 
Yellownefsof light is not a primary colour, but a compound 
of Red,&c. 
9. The laft Experiment was made in reference to Mr. New- 
tons 1 2 Pr^^^^where from his own principles he renders a very 
plaufible Reafon of ^(nr\iU2mgPh<ef9omemn ^ related by Mr. 
Hookci namely of two liquors, the one Blew, the other Red, 
both feverally tranfparenr, yet both, if placed together, be- 
came opake. The reafon whereof, faith Mr. Newton^ is , be- 
caufe if one liquor tranfmitted only Red, the other only Blew, 
no rays could pafs through both. 
In reference then to this point , 1 filled two fmal! GlafTes 
with flat poliflied bottoms, the one with Aqua for tk ^ deeply 
died Blew ; the other with Oy 1 of turpentine^ died Red 5 both 
to that degree, as to reprefent all objefts through them refpe- 
aively Blew or Red. Then placing the one upon the other , I 
was able to difcern feveral bodies through both : whereas ac- 
cording to Mr. Theory, no objed: fliould appear 
throughboth Liquors ; becaufeif one tranfmit only Red, the 
other only Blew, no rays can pafs through both. 
Thefe Experimental Exceptions will not, I hope, be un- 
welcome ioW. Newton^ his only aim being the improvement 
of Natural knowledge^as it is alfo of, 
Sir, 
Your bumble Servant, 
Anthony Lucas* 
Yyyy t Poft" 
