Subtile or Aetherial MEDIUM. Sir Isaac Newton considers it probable, that, beside the particular aereal medium, wherein we live and breathe, there is another more universal one, which he calls an aetherial medium; vastly more rare, subtile, elastic, and active, than air; and by that means freely permeating the pores and interstices of all other mediums, and diffusing itself through the whole creation; and by the intervention hereof he thinks it is that most of the great phenomena of nature are effected. See ETHER, ELECTRICITY, FIRE, &c.