that Light beyond the end of that stream which was behind the Knife, and
looking towards the Knife, I could see a line of Light upon its edge,
and that not only when my Eye was in the line of the Streams, but also
when it was without that line either towards the point of the Knife, or
towards the handle. This line of Light appear'd contiguous to the edge
of the Knife, and was narrower than the Light of the innermost Fringe,
and narrowest when my Eye was farthest from the direct Light, and
therefore seem'd to pass between the Light of that Fringe and the edge
of the Knife, and that which passed nearest the edge to be most bent,
though not all of it.
_Obs._ 6. I placed another Knife by this, so that their edges might be
parallel, and look towards one another, and that the beam of Light might
fall upon both the Knives, and some part of it pass between their edges.
And when the distance of their edges was about the 400th part of an
Inch, the stream parted in the middle, and left a Shadow between the two
parts. This Shadow was so black and dark that all the Light which passed
between the Knives seem'd to be bent, and turn'd aside to the one hand
or to the other. And as the Knives still approach'd one another the
Shadow grew broader, and the streams shorter at their inward ends which
were next the Shadow, until upon the contact of the Knives the whole
Light vanish'd, leaving its place to the Shadow.
And hence I gather that the Light which is least bent, and goes to the
inward ends of the streams, passes by the edges of the Knives at the
greatest distance, and this distance when the Shadow begins to appear
between the streams, is about the 800th part of an Inch. And the Light
which passes by the edges of the Knives at distances still less and
less, is more and more bent, and goes to those parts of the streams
which are farther and farther from the direct Light; because when the
Knives approach one another till they touch, those parts of the streams
vanish last which are farthest from the direct Light.
_Obs._ 7. In the fifth Observation the Fringes did not appear, but by
reason of the breadth of the hole in the Window became so broad as to
run into one another, and by joining, to make one continued Light in the
beginning of the streams. But in the sixth, as the Knives approached one
another, a little before the Shadow appeared between the two streams,
the Fringes began to appear on the inner ends of the Streams on either
side of the direct Light; three on one side made by the edge of one
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