_Bodies reflect and refract Light by one and the same power, variously
exercised in various Circumstances._
This appears by several Considerations. First, Because when Light goes
out of Glass into Air, as obliquely as it can possibly do. If its
Incidence be made still more oblique, it becomes totally reflected. For
the power of the Glass after it has refracted the Light as obliquely as
is possible, if the Incidence be still made more oblique, becomes too
strong to let any of its Rays go through, and by consequence causes
total Reflexions. Secondly, Because Light is alternately reflected and
transmitted by thin Plates of Glass for many Successions, accordingly as
the thickness of the Plate increases in an arithmetical Progression. For
here the thickness of the Glass determines whether that Power by which
Glass acts upon Light shall cause it to be reflected, or suffer it to
be transmitted. And, Thirdly, because those Surfaces of transparent
Bodies which have the greatest refracting power, reflect the greatest
quantity of Light, as was shewn in the first Proposition.