_If any sort of Rays falling on the polite Surface of any pellucid
Medium be reflected back, the Fits of easy Reflexion, which they have at
the point of Reflexion, shall still continue to return; and the Returns
shall be at distances from the point of Reflexion in the arithmetical
progression of the Numbers 2, 4, 6, 8, 10, 12, &c. and between these
Fits the Rays shall be in Fits of easy Transmission._
For since the Fits of easy Reflexion and easy Transmission are of a
returning nature, there is no reason why these Fits, which continued
till the Ray arrived at the reflecting Medium, and there inclined the
Ray to Reflexion, should there cease. And if the Ray at the point of
Reflexion was in a Fit of easy Reflexion, the progression of the
distances of these Fits from that point must begin from 0, and so be of
the Numbers 0, 2, 4, 6, 8, &c. And therefore the progression of the
distances of the intermediate Fits of easy Transmission, reckon'd from
the same point, must be in the progression of the odd Numbers 1, 3, 5,
7, 9, &c. contrary to what happens when the Fits are propagated from
points of Refraction.