rop of Water. At the first
Reflexion of the Rays within the drop, some Colours ought to be
transmitted, as in the case of a Lens, and others to be reflected back
to the Eye. For instance, if the Diameter of a small drop or globule of
Water be about the 500th part of an Inch, so that a red-making Ray in
passing through the middle of this globule has 250 Fits of easy
Transmission within the globule, and that all the red-making Rays which
are at a certain distance from this middle Ray round about it have 249
Fits within the globule, and all the like Rays at a certain farther
distance round about it have 248 Fits, and all those at a certain
farther distance 247 Fits, and so on; these concentrick Circles of Rays
after their transmission, falling on a white Paper, will make
concentrick Rings of red upon the Paper, supposing the Light which
passes through one single globule, strong enough to be sensible. And, in
like manner, the Rays of other Colours will make Rings of other Colours.
Suppose now that in a fair Day the Sun shines through a thin Cloud of
such globules of Water or Hail, and that the globules are all of the
same bigness; and the Sun seen through this Cloud shall appear
encompassed with the like concentrick Rings of Colours, and the Diameter
of the first Ring of red shall be 7-1/4 Degrees, that of the second
10-1/4 Degrees, that of the third 12 Degrees 33 Minutes. And accordingly
as the Globules of Water are bigger or less, the Rings shall be less or
bigger. This is the Theory, and Experience answers it. For in _June_
1692, I saw by reflexion in a Vessel of stagnating Water three Halos,
Crowns, or Rings of Colours about the Sun, like three little Rain-bows,
concentrick to his Body. The Colours of the first or innermost Crown
were blue next the Sun, red without, and white in the middle between the
blue and red. Those of the second Crown were purple and blue within, and
pale red without, and green in the middle. And those of the third were
pale blue within, and pale red without; these Crowns enclosed one
another immediately, so that their Colours proceeded in this continual
order from the Sun outward: blue, white, red; purple, blue, green, pale
yellow and red; pale blue, pale red. The Diameter of the second Crown
measured from the middle of the yellow and red on one side of the Sun,
to the middle of the same Colour on the other side was 9-1/3 Degrees, or
thereabouts. The Diameters of the first and third I had not time