e received from the
sun in a single day for the whole globe, and we shall find that nothing
but a material medium will suffice to convey this force.

Let us appeal to analogy. The undulations of our atmosphere produce
sound; that is, convey to the ear a part of a mechanical force imparted
to a solid body--a bell for instance. Let us suppose this force to equal
one pound. On account of the elasticity of the bell, the whole of the
force is not instantaneously imparted to the surrounding air; but the
denser the air the sooner it loses its motion. In a dense fluid like
water, the motion is imparted quickly, and the sound is not a ring but a
click. If we diminish the density of the air, the loss of motion is
retarded; so that we might conceive it possible, provided the bell could
be suspended in a _perfect vacuum_, without a mechanical tie, and there
was no friction to overcome from the rigidity of its particles, that the
bell would vibrate forever, although its sound could never reach the
ear. We see, therefore, that the mechanical effect in a given time, is
owing to the density of the medium. But can we resort to such an
analogy? Every discovery in the science confirms more and more the
analogy between the motions of air and the medium of space; the angle of
reflexion and incidence follows the same law in both; the law of
radiation and interference; and if experiments were instituted, there
can be but little doubt that sound has also got its spectrum.

ETHER IMPONDERABLE.

The medium of space, therefore, is capable of conveying a mechanical
force from one body to another; it therefore possesses inertia. Does it
also possess gravity? If we forsake not the principles of science, it is
but right that we expect science shall abide by her own principles.
Condensation in every elastic medium is as the compressing power,
according to all experiments. In the case of our atmosphere under the
law of gravitation, the density of air, (supposing it to be infinitely
expansible,) at a height only of ten semidiameters of the earth above
its surface, would have only a density equal to the density of one cubic
inch of such air we breathe, if that cubic inch was to be expanded so as
to fill a globular space whose centre should be the earth, and whose
surface should take inside the whole visible creation. Such a medium
could convey no mechanical force from the sun, and therefore the medium
of space cannot be ponderable. Simple as the argu