white, yellow, and red) of the first | |
Fringe | 1/170 | 1/32
-------------------------------------------+-----------+--------
The breadth of the darker Space between | |
the first and second Fringes | 1/240 | 1/45
-------------------------------------------+-----------+--------
The breadth of the luminous Part of the | |
second Fringe | 1/290 | 1/55
-------------------------------------------+-----------+--------
The breadth of the darker Space between | |
the second and third Fringes | 1/340 | 1/63
-------------------------------------------+-----------+--------
These Measures I took by letting the Shadow of the Hair, at half a Foot
distance, fall so obliquely on the Scale, as to appear twelve times
broader than when it fell perpendicularly on it at the same distance,
and setting down in this Table the twelfth part of the Measures I then
took.
_Obs._ 4. When the Shadow and Fringes were cast obliquely upon a smooth
white Body, and that Body was removed farther and farther from the Hair,
the first Fringe began to appear and look brighter than the rest of the
Light at the distance of less than a quarter of an Inch from the Hair,
and the dark Line or Shadow between that and the second Fringe began to
appear at a less distance from the Hair than that of the third part of
an Inch. The second Fringe began to appear at a distance from the Hair
of less than half an Inch, and the Shadow between that and the third
Fringe at a distance less than an inch, and the third Fringe at a
distance less than three Inches. At greater distances they became much
more sensible, but kept very nearly the same proportion of their
breadths and intervals which they had at their first appearing. For the
distance between the middle of the first, and middle of the second
Fringe, was to the distance between the middle of the second and middle
of the third Fringe, as three to two, or ten to seven. And the last of
these two distances was equal to the breadth of the bright Light or
luminous part of the first Fringe. And this breadth was to the breadth
of the bright Light of the second Fringe as seven to four, and to the
dark Interval of the first and second Fringe as three to two, and to
the like dark Interval between the second and third as two to one. For
the breadths of the Fringes seem'd to be in the progression of the
184