plane n.

While vibration ceases to affect our senses at 40,000 vibrations per second as sound, we find ourselves conscious again of periodic motion when it reaches 398 trillion times per second; then we hear with our eyes, or see with our ears, whichever you choose. The sensation is in all cases the effect of motion. There is much food for thought, or speculation in the thought that there exist sound-waves that no ear can hear, and color-waves that no eye can see. The (to us) long, dark, soundless space between 40,000 and 398 trillions, and the infinity of range beyond 764 trillions, where light ceases in the universe of motion, makes it possible to indulge in the speculation that there may be beings who live in different planes from ourselves, and who are endowed with sense-organs like our own, only they are tuned to hear and see in a different sphere of motion.

Though now more or less accustomed to the sensation of being transported, as it were, into this mysterious other plane, I could not refrain from instinctively crying out when the herd of beasts suddenly stampeded in my direction. I twas hard to realize that I had no existence for them; that I was so much space through which they sped like a whirlwind and were gone.

Our scientists call them plains [sic]…. But they are really worlds coexistent with this one.

Sutter walked forward slowly, aware in a vague way that he had entered another plane that was at once a microcosm and a macrocosm.

If you walk in front of a mirror in this plane, the other you will do the same thing in the other plane.

A society in harmonious tune with the Universe, capable of perceiving multiple planes of existence, travelling at multiples of the speed of light.

Cap learned his father was from Merlin’s home plane, Otherworld.

The London of the alternate plane in which Everett finds himself for the majority of the story is quite a fascinating and even enticing creation, a kind of pseudo-Victorian London in feel and street-level life, like steampunk.