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.