although the discontinuity is as invisible to the eye in the latter case
as in the former.

Without following this out any farther, however, the point may be here
emphasized that it is hardly possible for one who, like the majority of
physicists, regards matter as molecular and energy as a continuum, to hold
the same ideas regarding the identity of the two. Efforts to show that
definite portions of energy, like definite portions of matter, retain
their identity have hitherto been made chiefly on the lines of a
demonstration that energy travels by definite and continuous paths in
space just as matter does. This is very well, but it would appear to be
necessary to supplement it with evidence to show that the lines
representing these paths do not form at their intersections continuous
blurs that not only forbid any practical attempt at identification on
emergence, but make it doubtful whether we can in any true sense call the
issuing path identical with the entering one. Otherwise the identity of
energy can be admitted to be only that kind of identity that could be
preserved by matter if its molecular structure did not exist. One who can
admit that this sort of identity is the same sort that can be preserved by
molecular matter may be able to hold the identity of energy in the present
state of the evidence, but the present attitude of physicists would seem
to show that, whether they realize the connection of the two subjects or
not, they cannot take this view. In other words, modern views of the
identity of matter seem closely connected with modern views of its
structure, and the same connection will doubtless hold good for energy.

Regarding the probable success of an attempt to prove that energy has a
"structure" analogous to the molecular structure of matter, any prediction
would doubtless be rash just now. The writer has been unable, up to the
present time, to disprove the proposition, but the subject is one of