tracted some attention, "particularly," says one writer, "among the followers of Hegel, and mathematicians who hold to the actual existence of a so-called non-Euclidean space—that is to say, of space which has more dimensions than length, breadth, and thickness—space in which it would be possible to tie a knot in an endless cord and to turn a rubber ball inside out without 'a solution of its continuity,' or in other words, without breaking or cracking it."
Dr. Hern believes that in the visible world there are void places—vacua, and something more—holes, as it were, through which animate and inanimate objects may fall into the invisible world and be seen and heard no more. The theory is something like this: Space is pervaded by luminiferous ether, which is a material thing—as much a substance as air or water, though almost infinitely more attenuated. All force, all forms of energy must be propagated in this; every process must take place in it which takes place at all. But let us suppose that cavities exist in this otherwise universal medium, as caverns exist in the earth, or cells in a Swiss cheese. In such a cavity there would be absolutely nothing. It would be such a vacuum as cannot
