o
the Glass, they shall be in great measure transmitted where the Water is
adjacent to it; which argues, that their Reflexion or Transmission
depends on the constitution of the Air and Water behind the Glass, and
not on the striking of the Rays upon the parts of the Glass. Thirdly,
If the Colours made by a Prism placed at the entrance of a Beam of Light
into a darken'd Room be successively cast on a second Prism placed at a
greater distance from the former, in such manner that they are all alike
incident upon it, the second Prism may be so inclined to the incident
Rays, that those which are of a blue Colour shall be all reflected by
it, and yet those of a red Colour pretty copiously transmitted. Now if
the Reflexion be caused by the parts of Air or Glass, I would ask, why
at the same Obliquity of Incidence the blue should wholly impinge on
those parts, so as to be all reflected, and yet the red find Pores
enough to be in a great measure transmitted. Fourthly, Where two Glasses
touch one another, there is no sensible Reflexion, as was declared in
the first Observation; and yet I see no reason why the Rays should not
impinge on the parts of Glass, as much when contiguous to other Glass as
when contiguous to Air. Fifthly, When the top of a Water-Bubble (in the
17th Observation,) by the continual subsiding and exhaling of the Water
grew very thin, there was such a little and almost insensible quantity
of Light reflected from it, that it appeared intensely black; whereas
round about that black Spot, where the Water was thicker, the Reflexion
was so strong as to make the Water seem very white. Nor is it only at
the least thickness of thin Plates or Bubbles, that there is no manifest
Reflexion, but at many other thicknesses continually greater and
greater. For in the 15th Observation the Rays of the same Colour were by
turns transmitted at one thickness, and reflected at another thickness,
for an indeterminate number of Successions. And yet in the Superficies
of the thinned Body, where it is of any one thickness, there are as many
parts for the Rays to impinge on, as where it is of any other thickness.
Sixthly, If Reflexion were caused by the parts of reflecting Bodies, it
would be impossible for thin Plates or Bubbles, at one and the same
place, to reflect the Rays of one Colour, and transmit those of another,
as they do according to the 13th and 15th Observations. For it is not to
be imagined that at one place the Rays which,