please, and thereby know that these curve lines are
Hyperbola's differing little from the conical Hyperbola. And by
measuring the lines C_i_, C_k_, C_l_, you may find other points of these
Curves.

For instance; when the Knives were distant from the hole in the Window
ten Feet, and the Paper from the Knives nine Feet, and the Angle
contained by the edges of the Knives to which the Angle ACB is equal,
was subtended by a Chord which was to the Radius as 1 to 32, and the
distance of the line _rv_ from the Asymptote DE was half an Inch: I
measured the lines _ps_, _qt_, _rv_, and found them 0'35, 0'65, 0'98
Inches respectively; and by adding to their halfs the line 1/2 _mn_,
(which here was the 128th part of an Inch, or 0'0078 Inches,) the Sums
_np_, _nq_, _nr_, were 0'1828, 0'3328, 0'4978 Inches. I measured also
the distances of the brightest parts of the Fringes which run between
_pq_ and _st_, _qr_ and _tv_, and next beyond _r_ and _v_, and found
them 0'5, 0'8, and 1'17 Inches.

_Obs._ 11. The Sun shining into my darken'd Room through a small round
hole made in a Plate of Lead with a slender Pin, as above; I placed at
the hole a Prism to refract the Light, and form on the opposite Wall the
Spectrum of Colours, described in the third Experiment of the first
Book. And then I found that the Shadows of all Bodies held in the
colour'd Light between the Prism and the Wall, were border'd with
Fringes of the Colour of that Light in which they were held. In the full
red Light they were totally red without any sensible blue or violet, and
in the deep blue Light they were totally blue without any sensible red
or yellow; and so in the green Light they were totally green, excepting
a little yellow and blue, which were mixed in the green Light of the
Prism. And comparing the Fringes made in the several colour'd Lights, I
found that those made in the red Light were largest, those made in the
violet were least, and those made in the green were of a middle bigness.
For the Fringes with which the Shadow of a Man's Hair were bordered,
being measured cross the Shadow at the distance of six Inches from the
Hair, the distance between the middle and most luminous part of the
first or innermost Fringe on one side of the Shadow, and that of the
like Fringe on the other side of the Shadow, was in the full red Light
1/37-1/4 of an Inch, and in the full violet 7/46. And the like distance
between the middle and most luminous parts of the second Frin