microscope, as though a four-dimensional figure were registering its
passage through our space.


THE ELECTRIC CURRENT

Hinton conceived of an electric current as a four-dimensional vortex.
He declared that on the Higher Space Hypothesis the revolution of
the ether would yield the phenomenon of the electric current. The
reader is referred to Hinton's book, _The Fourth Dimension_, for an
extended development of this idea. What follows is a brief summary
of his argument. First, he examines the characteristics of a vortex
in a three-dimensional fluid. Then he conceives of what such a
vortex would be in a four-dimensional medium of analogous properties.
The whirl would be about a _plane_, and the contour of this plane
would correspond to the ends of the axis line in the former vortex;
and as before, the vortex would extend to the boundary. Every
electric current forms a closed circuit: this is equivalent to the
hyper-vortex having its ends in the boundary of the hyper-fluid. The
vortex with a _surface_ as its axis, therefore, affords a geometric
image of a closed circuit.

Hinton supposes a conductor to be a body which has the property
of serving as a terminal abutment to such a hyper-vortex as has
been described. The conception that he forms of a closed current,
therefore, is of a vortex sheet having its _edge_ along the
circuit of the conducting wire. The whole wire would then be like
the centers on which a spindle turns in three-dimensional space,
and any interruption of the continuity of the wire would produce
a _tension_ in place of a continuous revolution. The phenomena