( 3©^3 ) 
not coo far difta^t one from another, they by their mntual alloy 
compound that colour, which in the faid feries appeareth in the 
mid^ way between them> But thofe, which are fitoated ac too 
^r<;at a diftapce, do not fo. Orange gind Indico ^voducz not the 
rntermediate Green ^ nor Scarlet and Green the intermediate 
yellow. 
7. Buttheraoftfurprifing.and wonderful compoficion was that 
of Whitemfs^ There is no one fort of Rays which alone can ex- 
hibit this. Tis ever compounded,aod to its corapofition are re- 
quilite all the aforefaid primary Colours, mixed in a due propor^ 
tion. I have often with Admiration beheld, that all the Colours 
of the Prifme being made to converge, and thereby to be agaia 
mixed as they were in the light before ic was Incident upon the 
Prifme, reproduced light, intirely and perf ed:Iy white, and noc 
at all fenfibly differing from a direB Light of the Sun , unlefs 
when the glaffes, I ufedjWere not fufficiently clear j for then they 
would a little incline it to their colour. 
8. Hence therefore it comes to ^^U^ihztWhitenefs is the ufual co« 
lour oi Light 5 for. Light is a confufed aggregate of Rays indued 
with all forts of Colors^as they are promilcuoufly darted from the 
various parts of luminous bodies* And of fuch a confufed aggre- 
gate^as I faid, is generated Whitenefs, if there be a due proporti- 
on of the Ingredients 5 but if any one predominate^ch^ Light muft 
incline to that colour ^ as it happens in the Blew flame of Brim* 
ftone ; the yellow flame of a Candle j and the various coiours of 
the Fixed ftars. 
9. Thefe things confidered J the manner ^ 1k)w colours are pro- 
duced by the Prifme, is evident. For, of the Rays, conftituting 
the incident Hght, fince thofe which difTer in Colour proportio - 
nally differ in RefrangibiHty , they by their unequall refraftions 
muft be fevered and difperfed into an oblong form in an orderly 
fucceffion from the leaft refraded Scarlet to the moft refra&ed 
Violet. And for the fame reafon it is, that objefts, when looked 
upon through a Prifme,appear coloured. Forjthe difform Rays, 
by their unequal Refrad:ions, are made to diverge towards fe- 
vera! parts ojf thQ Retina^ and there exprefs the Images of things 
coloured, as in the former cafe they did the Suns Image upon a 
wall. And by this inequality of refraitions they become not 
only coloured, but alfo very confufed and indiflindt 
I©. Why the Colours of the Rainbow appear in falling drops 
Hhhh of 
