Opticks 1717 - Up

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in the Superficies of the thinned Body, where
it is of any one thicknef~, there ark as many
parts for the Rays to impinge on< AS where it,
is ef ally other thiclmel2. Sixthl. , Tf Reflexion ti
~7ere ca~&d by the parts of wf- T e&ing Bodies,
it would be impofflble for thin Plates or Bubbles
at one and the fame place to A-k& the x
1 Rays of one Colour and tranfmit thok of another,
as they do according to the 13th end I stlz
Obfervations. For it is not to be ima iiwd
that al: 011~ pine the Rays which for ini F ancc
cxljibit x blue CO~OLK, fhould ~NVC the fortune
to dllfll up011 the pm, and thok which exhibit
:I wd to ,hit upon the POWS Of the Ro+dy ;
and then at mother pl~e, where the Body is
tither a little thicker, or a little thinner, that
on the ‘contrary the blue’ kould hit upon its
pores, and the red upon its parts. L:litly, were
the Rays of L,iglTt reflckkd by impinging on
the folid parts of Bodies, their Rcflcxions from
p~liifn’d Bodies could not be TO regular ils they
~2-2. I;lor in poliihing Gluts kth Sand, Putty or
‘I’t-ipoly, it is not to bc inqined that thok
Sul31tatms can hv grating and fretting chc Glafs
bring all its leafi Particlcs to an accurate Pal& ;
ii, that all their Surfi~ccs flmll bc truly pla~ii 02
truly f$wical , and loo!; all the fame wqy, fcr
as together to compofc OllC CQ*Cll $~urfilcc. The
iinnllcr the Particles of tholk Subitanccr; we9
tl?c findlcr will 1x2 the Scratches by whi‘ch they
cor~cinu~~ll\i fret and wew awaj7 the GM!; rmnl
it bc poliih’d ,. but be they iievc~ Co linall they
cm zvcar away the C&Ii‘s no othc~wifc than by
grating Xlcl iClXtChi1~~ ilt ,’ alld brtsliing the
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