er, nor did it encroach on the magnetic domain: only
vague similarities in the phenomena of attraction and repulsion aroused
attention. But directly electricity was set in motion, constituting
what is called an electric current, magnetic lines of force instantly
sprang into being, without the presence of any steel or iron; and in
twenty years they were recognised. These electrically generated lines
of force are similar to those previously known, but they need no matter
to sustain them. They need matter to display them, but they themselves
exist equally well in perfect vacuum.

How did they manage to spring into being? Can it be said that they too
had existed previously in some dormant condition in the ether of space?
That they too were closed loops opened out, and their existence thus
displayed, by the electric current?

That is an assertion which might reasonably be made: it is not the only
way of regarding the matter, however, and the mode in which a magnetic
field originates round the path of a moving charge--being generated
during the acceleration-period by a pulse of radiation which travels
with the speed of light, being maintained during the steady-motion
period by a sort of inertia as if in accordance with the first law of
motion, and being destroyed only by a return pulse of re-radiation
during a retardation-period when the moving charge is stopped or
diverted or reversed--all this can hardly be fully explained until the
intimate nature of an electric charge has been more fully worked out;
and the subject now trenches too nearly on the more advanced parts of
Physics to be useful any longer as an analogue for general readers.

Indeed it must be recollected that no analogy will bear pressing too
far. All that we are concerned to show is that known magnetic behaviour
exhibits a very fair analogy to some aspects of that still more
mysterious entity which we call "life"; and if anyone should assert
that all magnetism was pre-existent in some ethereal condition, that it
would never go out of essential existence, but that it could be brought
into relation with the world of matter by certain acts,--that while
there it could operate in a certain way, controlling the motion of
bodies, interacting with forms of energy, producing sundry effects for
a time, and then disappearing from our ken to the immaterial region
whence it came,--he would be saying what no physicist would think it
worth while to object to, what many ind