05, vol. ii. p. 526).
On the other hand, the well-known physicist Dr A.H. Bucherer, speaking
at the Naturforscherversammlung, held at Stuttgart in 1906, declared
his disbelief in the existence of the ether, which he thought could
not be reconciled at once with the Maxwellian theory and the known
facts.--ED.]

It was the study of the phenomena of polarization which led Fresnel to
his bold conception of transverse vibrations, and subsequently induced
him to penetrate further into the constitution of the ether. We know
the experiment of Arago on the noninterference of polarized rays in
rectangular planes. While two systems of waves, proceeding from the
same source of natural light and propagating themselves in nearly
parallel directions, increase or become destroyed according to whether
the nature of the superposed waves are of the same or of contrary
signs, the waves of the rays polarized in perpendicular planes, on the
other hand, can never interfere with each other. Whatever the
difference of their course, the intensity of the light is always the
sum of the intensity of the two rays.

Fresnel perceived that this experiment absolutely compels us to reject
the hypothesis of longitudinal vibrations acting along the line of
propagation in the direction of the rays. To explain it, it must of
necessity be admitted, on the contrary, that the vibrations are
transverse and perpendicular to the ray. Verdet could say, in all
truth, "It is not possible to deny the transverse direction of
luminous vibrations, without at the same time denying that light
consists of an undulatory movement."

Such vibrations do not and cannot exist in any medium resembling a
fluid. The characteristic of a fluid is that its different parts can
displace themselves with regard to one another without any reaction
appearing so long as a variation of volume is not produced. There
certainly may exist, as we have seen, certain traces of rigidity in a
liquid, but we cannot conceive such a thing in a body infinitely more
subtle than rarefied gas. Among material bodies, a solid alone really
possesses the rigidity sufficient for the production within it of
transverse vibrations and for their maintenance during their
propagation.

Since we have to attribute such a property to the ether, we may add
that on this point it resembles a solid, and Lord Kelvin has shown
that this solid, would be much more rigid than steel. This conclusion
produces great surprise in