example, the heat which causes a kilogramme
of water to rise a degree centigrade in
temperature, will, if converted into motion,
produce a mechanical force capable of raising
about four hundred and thirty kilogrammes
the height of a metre in a second of time; so
that four hundred and thirty is the mechanical
equivalent of heat. If we could only
rigorously determine the equivalents of
the other forces of nature, what an immense
stride would science have made, and what a
vast field would thus be opened to the research
of the rising generation! Even now, by showing
us how slight an elevation of temperature
is necessary to produce a considerable
mechanical effort, the mechanical equivalent
of heat has taught us that we burn twenty
times too much coal in the furnaces of our
present steam-engines, and that we must
invent others on a new plan. By applying
these ideas, Monsieur Seguin has been led to
construct his Pulmonary Steam-engine, and
Monsieur Siemens his Regenerated Steam-
engine.

To the correlation of the forces already
known, there seems to be no end or limit;
that other forces may yet be discovered;
differing as much from those known as they
differ from each other, is highly probable;
and that when discovered, and their modes of
action fully traced out, they will be found
reciprocally related on one general and
harmonious plan, may be believed to be as far
certain as certainty can be predicted of any
future event. Thus, sound is motion; and
although at the close of the last century a theory
was advanced that sound was transmitted by
the vibrations of an ether, we now so readily
resolve sound into motion, that to those
who are familiar with acoustics, the phenomena
of sound immediately present to the
mind the idea of motion, that is, motion of
ordinary matter. Again: no doubt now
exists that light moves, or is accompanied by
motion. Here the phenomena of motion are
not made evident by ordinary sensuous
perception: as all observation teaches us that
bodies, in moving from one point in space
to another, occupy time, we conclude that,
wherever a continuing phenomenon is
rendered evident in two different points of space
at different times, there is motion, though we
cannot see the progression. A similar deduction
convinces us of the motion of electricity.
Of absolute rest nature gives no evidence:
all matter, as far as we can ascertain, is ever
in movement, not merely in masses, as with
the planetary spheres, but also molecularly,
or throughout its most intimate structure.
Thus, every alteration of temperature
produces a molecular change throughout the
whole substance, heated or cooled; slow
chemical or electrical actions, actions of light
or invisible radiant forces, are always at play,
so that as a fact we cannot predicate of any
portion of matter that it is absolutely at
rest.

Mr. Smee thinks, even, that odours constitute
a further range of actions and reactions;
in which view he feels the more confirmed
the more he watches those animals, as the
bloodhound, which have the nerves of the
nose highly developed. Upon this matter,
however, we are much in the same position
as the man born blind, who can only receive
his ideas of light through the medium of the
eyes of others; for man has literally only a
rudimentary nose, if it be compared with that
of other animals.

The fundamental and radical unity of all
the natural forces promises even to supply a
bridge which shall enable us to make a road
across that profound gulf which yawns
between physics and metaphysics. The history
of the human race proves every hour, that
of the three grand manifestations of the
Creative Power—space, matter, and time—
the one which we comprehend the least in its
essence, and whose future effects are the
most difficult to divine and even to guess at,
is the last, namely, time. But time itself,
as a phenomenon, is now drawn by Mr. Smee
into the vortex of physical science. For let
us suppose that a change of matter could
take place without time; the coals in our
grates would be consumed instantly; if our
house caught fire, the whole would
momentarily vanish; if we set any body in motion,
however gently, it would arrive at its
destination quicker than thought, and be
dashed to pieces. Chemistry supplies us
with substances, the particles of which are
held together so slightly, that upon the
slightest application of force, they are
separated; iodide of nitrogen, for instance,
separates upon the slightest agitation into its
component parts. The safety of the proper
use of gunpowder depends upon its
progressive action, which is slow as compared
with iodide of nitrogen, or with some varieties
of gun cotton.

Man derives the idea of time from the
resistance to change; if the total changes
constituting an event are performed with
energy, but little time is occupied; if the
resistance to change is great, considerable
time is evinced. The sum total of all time
is the representation of all the events which
have happened from the commencement of
matter to the present moment; and the
number of revolutions of the earth round the
sun, or of the earth upon its axis, are
generally the events which are counted as our
measure of time. But, from the very nature
of time, one event preceded all subsequent
events, namely, the first rushing together or
attraction of particles of matter, which gave
to every object its composition, form, and
position, and which we usually understand
by the word Creation.

From these views we find that time can
have none, no, not even the feeblest quality of
eternity; and that however exaggeratedly
it may be increased, time never becomes