An ink spot on the handkerchief becomes the Time Gate. By folding the handkerchief that spot may be superposed on any other spot on the silk. Press the two spots together between thumb and forefinger; the controls are set, the Time Gate is open, a microscopic inhabitant of this piece of silk may crawl from one fold to the other without traversing any other part of the cloth.
The model is imperfect; the picture is static―but a physical picture is necessarily limited by the sensory experience of the person visualizing it.
He could not make up his mind whether or not the concept of folding the four-dimensional continuum―three of space, one of time-back on itself so that the Gate was "open" required the concept of higher dimensions through which to fold it. It seemed so, yet it might simply be an intellectual shortcoming of the human mind. Nothing but empty space was required for the "folding," but "empty space" was itself a term totally lacking in meaning―he was enough of a mathematician to know that.
If higher dimensions were required to "hold" a four-dimensional continuum, then the number of dimensions of space and of time were necessarily infinite; each order requires the next higher order to maintain it.
But "infinite" was another meaningless term. "Open series" was a little better, but not much.
Another consideration forced him to conclude that there was probably at least one more dimension than the four his senses could perceive―the Time Gate itself. He became quite skilled in handling its controls, but he never acquired the foggiest notion of how it worked, or how it had been built. It seemed to him that the creatures who built it must necessarily have been able to stand outside the limits that confined him in order to anchor the Gate to the structure of space time. The concept escaped him.
He suspected that the controls he saw were simply the ones that stuck through into the space he knew. The very palace itself might be no more than a three-dimensional section of a more involved structure. Such a condition would help to explain the otherwise inexplicable nature of its architecture.
He became possessed of an overpowering desire to know more about these strange creatures, the "High Ones," who had come and ruled the human race and built this palace and this Gate, and gone away again―and in whose backwash he had been flung out of his setting some thirty millennia. To the human race they were no more than a sacred myth, a contradictory mass of tradition. No picture of them remained, no trace of their writing, nothing of their works save the High Palace of Norkaal and the Gate. And a sense of irreparable loss in the hearts of the race they had ruled, a loss expressed by their own term for themselves―the Forsaken Ones.
With controls and speculum he hunted back through time, seeking the Builders. It was slow work, as he had found before. A passing shadow, a tedious retracing―and failure.
Once he was sure that he had seen such a shadow in the speculum. He set the controls back far enough to be sure that he had repassed it, armed himself with food and drink and waited.