Opticks 1717 - Up

I
GX;hX, IX, qX, EX, yX3 aX’MX,tobe
in proportion to one ano!her, as the numbers,
9
I, 4, -;, 4, 4, -;, 77) ;, and fo CO reprefent the
Thor& of the Key, and of a rrone, a thirdi!&-
n~r, a fourth, a fifth, a fisth Major, a feventh
and & eighth above that Key: And the IlIter&
vals h/ICC, ayy YE> E% r,‘, bb and AG, will be
the Spaces which &e iev~d CO~OUE (red, .o-
.range, ydow , green, blue , indigo, violet)
take up.
: how thefe Intervals or Spaces fubtending the
di$&ences of the ‘Refra&ions of the Rays goi
ilig to the limits of thofe CO~OUJYS, thas. is, lo
the Points M, a, y9 E) Q 1) A, G, may withdut:
any fenfible Error be accqun’ted proportional
to the diffkrences of the Sines of RefraAion of
tl!ofe Rays having one common Sine of Incidence,
and therefore fince the common Sine of
@cidence of the rnofi; and leafi refrangibIe Rays
out of Glafs into A.ir was (by a method dekri-
bed above) found is proportion to their Sines
of Refix&ion, as 5~ to 77 and 78, divide the
$fference between the Sines of Refra&ion 77
and 78, as the Line G i?+4 is divided by thofe
Intervals, you will have 77, 77& 774 77+, 77;;
77$, 772, 78, the Sines of Refix&on of thofe,
Rays out of Glai‘s into Air, their common -Sin&
of, Iacidence being ~0. So then the Sines of
yhe, Incidences of all the red-making Rays otic
of Glafs into Air, wefe to the Sines of their Re+
@a&ti’ons, not ‘greater than 50 to 77, nor. lefv
$an 50 to 77;; but they varied fro’m one an&
ther according to all intermediate roportions,
&nd “the Ekes &-the Tncidences Q the. .@ee$