Boyle's glass dome is empty, but light pervades it nevertheless. Doesn't light need a medium for propagation? Or is there a medium which is not sucked out by the air pump?

In his Optick Newton writes about that question: "When a Ray of light falls upon the surface of any pellucid body, and is there refracted or reflected: may not Waves of Vibrations, or Tremors, be thereby excited in the refracting or reflecting Medium at the point of Incidence, and continue to arise there, and to be propagated from thence as long as they continue to do so?"

Athanasius Kircher, Ars magna lucis et umbrae