MEDIUM

In Physics, the substance or matter in which bodies exist, or through which they move in pa ing from one point to another. The resistance which different mediums oppose to bodies in motion is proportional to the respective densities of the mediums. Newton supposed the existence of a universal medium, or ether, infinitely more rare and subtile than air, and diffused through the whole creation. The modern discoveries of the propagation of light by undulation, and ot the acceleration of some of the small comets, give great probability to this supposition. [s. 740]