Speed of light increased in water moving in the same direction as the light.

Tizeau found that the speed of light is increased in water which moves in the same direction as the light. This result must be due either to the motion of matter through the medium, or to the fact that moving matter carries the ether with it. The whole question of matter and motion as a medium is a vital one, and we shall hardly make any serious advance before experiment has found a new opening.