Opticks 1717 - Up

falling on that other Paper. This Image 9 t COII~
fiiis of Circles placed one after another in a re-
&linear order, as was fufhciently explained in
the fifth Experiment ; and thefe Circles are e-
qual to tile Circle Jg and confcqucntly anfwer
in. magnitude to the hole F ; and therefore by
diminiG$rg that hole they may be at pleafire
&n&ifl~ed, whilfi their centers remain in their
places. I3y this means 1 made the breadth of
the Image’p t to be forty times, and fometimcs
fixty or fcventy times Iefs than its Iength. As for
~inftnnce, if the breadth of the hole I? be one tenth
of an lunch, arid &IF’ the diikmce of the Lens from
ihe hole be 12 Feet ; and if p B or p. A4 the difiance
of the Image p t from the Prifm or Lens
be IQ Feet, and the refra&ing Angle of the
Prifrn b,e 62 Degrees, the breadth of the I-
mage p. L will be one twelfth of an Inch and the
length &out Cx Inches, and therefore the
length to the breadth as 72 to P, and by confequcnce
the Light of this Image 71 times lefi
compound than the Sun’s dire& Light. And
Light thus far Gmple and homogeneal, is furIicient
for trying all the Experiments in this Rook
about firnple Light. For the compofition of
heterogeneal Rays is in this Light fo little that
it is fcarce to ,be difcovered and perceived by
.Senfe, except ‘perhaps in the indigo and violet.
For thefe being dark Colours, do caiily
:iuffer a fenNAe allay by that little fcattering’
‘Light which ufcs to be reka&ed irregularly by
the inequalities of the Prifm.
I?et +I-cad of the circular hole I?, ‘t-is better
!o fubktute an oblong hole fhaped like a long
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Baral-