Come now between this and the prelude to the latter half of the drama whose history this narrative is⁠—only scattering and necessarily fragmentary observations.

First⁠—the nature of the ebon opacities, blocking out the spaces between the pavilion-pillars or covering their tops like roofs. These were magnetic fields, light absorbers, negativing the vibrations of radiance; literally screens of electric force which formed as impervious a barrier to light as would have screens of steel.

They instantaneously made night appear in a place where no night was. But they interposed no obstacle to air or to sound. They were extremely simple in their inception⁠—no more miraculous than is glass, which, inversely, admits the vibrations of light, but shuts out those coarser ones we call air⁠—and, partly, those others which produce upon our auditory nerves the effects we call sound.

Briefly their mechanism was this: