that the Light may be refracted in every Point of its Passage, and by
continual Refractions bent into a Curve-Line. And therefore the whole
Refraction of Light in passing through the Atmosphere from the highest
and rarest Part thereof down to the lowest and densest Part, must be
equal to the Refraction which it would suffer in passing at like
Obliquity out of a Vacuum immediately into Air of equal Density with