The Summary of Physics Restored

204A transparent body such as glass, when struck by the Sun’s rays, gathers them and receives the Sun’s image within itself. It becomes luminous and, as it were, a Sun in miniature, emitting rays of its own towards the farther side facing away from the Sun. Thus the solar rays, refracted by their encounter with the glass, appear to pass through and penetrate the glass itself. Yet this does not really happen: because of the air adhering to them, the rays are stopped at the glass and only the spirit of light is transmitted. The rays poured out on the other side are rays of a glassy Sun, or of glass kindled into a luminous body by the solar rays.