Opticks 1717 - Up

1)
86
thefe in ftrength are the red and green. rI’Y~a
blue compared with thef’e is a filint and dark
Colour, and the indigo and violet are much
darker and filinter, fo that thefe compared with
the U.rollger Colours are little to be regarded,
,Tlle Images of ObjeAs are therefore to be’plad,
not in the Focus of the mean refrangible’
ays which are in the con&x of green and.
blue, but in the I?ocus of thok Rays which are
in the middle of the orange and yellow; tliere
where the Colow is =moilt luminous and f;igent,
that is in the bri.ghteR yellow, that yellow wl$ch
&Iines more to orange
by the Refia&ion of tbel’e
Incidel?ce and RefracStion in Glafs are as 17and
II) ‘the Refra&ion of Glafs and Cry4-tal fo,r optical
Vies is to be meafured. Let us therefore
place the Image of tl!e Ob-je& in the E’ocus c$
thefe Rays, and all the yellow and orange will
fall within a Ci.rcle, whofe diameter is about .
the zyorh @l-t of the diameter of the Aperture
of the Glalk. Arid if you add the brighter half
,of the red, (that half which is next the orange)
+~nd the biighter half of the green, (that IraP
whicjl. is. next the yellow) about three Ififth
parts of tl:x Light of thcfe two Calours will
$21 within the fame Circle, .and two fifth parts‘
~41 fall without it round about .; and that which*
falls without will. ‘be Spread through almofi as
much more i‘pace as that which# &lls within, I’
and i:c! ill the grofs be alm’ofi thr$e t2nks rqrer.
-Of the ofther llalf of the red an$ green, (that is
pf the .deep dark ied and tiillow green) about
$$c guarter ,..., will T fiil1
..’ within I ,_:, this .,’.Circle’, and
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