th, includes depth likewise, is (wherever it be found)
_constructive agency_. That is but _one_ phenomenon of magnetism, to which
we have appropriated and confined the term magnetism; because of all the
natural bodies at present known, iron, and one or two of its nearest
relatives in the family of hard yet coherent metals, are the only ones, in
which all the conditions are collected, under which alone the magnetic
agency can appear in and during the act itself. When, therefore, I affirm
the power of reproduction in organized bodies to be magnetism, I must be
understood to mean that this power, as it exists in the magnet, and which
we there (to use a strong phrase) catch in the very act, is to the same
kind of power, working as reproductive, what the root is to the cube of
that root. We no more confound the force in the compass needle with that
of reproduction, than a man can be said to confound his liver with a
lichen, because he affirms that both of them grow.

The same precautions are to be repeated in the identification of
electricity with irritability; and the power of depth, for which we have
yet no appropriated term, with sensibility. How great the distance is in
all, and that the lowest degrees are adopted as the exponent terms, not
for their own sakes, but merely because they may be used with less hazard
of diverting the attention from the _kind_ by peculiar properties arising
out of the degree, is evident from the third instance, unless the theorist
can be supposed insane enough to apply sensation in good earnest to the
effervescence of an acid or an alkali, or to sympathise with the
distresses of a vat of new beer when it is working. In whatever way the
subject could be treated, it must have remained unintelligible to men who,
if they think of space at all, abstract their notion of it from the
contents of an exhausted receiver. With this, and with an ether, such men
may work wonders; as what, indeed, cannot be done with a plenum and a
vacuum, when a theorist has privileged himself to assume the one, or the
other, _ad libitum_?--in all innocence of heart, and undisturbed by the
reflection that the two things cannot both be true. That both time and
space are mere abstractions I am well aware; but I know with equal
certainty that what is _expressed_ by them as the _identity_ of both is
the highest reality, and the root of all power, the power to suffer, as
well as the power to act. However mere an _ens logicum_ spa