It evidently follows from all this that since the reflection and refraction of rays, or the deviation from the line of light pressures, is not produced by the gross parts of air in the ether, nor by those making up the lens, this deviation can result only from the centrifugal force of the vortexes of subtle matter by which they compress each other and all the bodies they surround in order to preserve equilibrium among contrary forces according to the natural law that all bodies move in the direction in which they are least pressed.