The dam was not over a mile or so from Larry's window; in his time it might have been the western end of Christopher Street. The moonlight shone on the massive metal of it: the water spilled through it in a dozen shining cascades. There was a low black metal structure perched halfway up the lower side of the dam, a few bluish lights showing through its windows. Though Larry did not know it then, this was the New York Power House. Great transformers were here, operated by turbines in the dam. The main power came over cables from Niagara: was transformed and altered here and sent into the air as radio-power for all the New York District.[3] [Footnote 3: In 2930, all aircraft engines were operated by radio-power transmitted by senders in various districts. The New York Power House controlled a local district of about two hundred miles radius.] Larry crossed his room to gaze through north and eastward windows. He saw now that the grounds of this three-story building of Tina's palace were surrounded by a ten-foot metal wall, along whose top were wires suggesting that it was electrified for defense. The garden lay just beneath Larry's north window. Through the tree branches the garden paths, beds of flowers and the fountains were visible. One-story palace wings partially enclosed the garden space, and outside was the electrified wall. The Time-traveling cage stood faintly shining in the dimness of the garden under the spreading foliage. * * * * * To the east, beyond the palace wall, there was an open garden of verdure crossed by a roadway. The nearest building was five hundred feet away. There was a small, barred gate in the palace walls beyond it. The road led to this other building--a squat, single-storied metal structure. This was a Government laboratory, operated by and in charge of Robots. It was almost square: two or three hundred feet in length and no more than thirty feet high, with a flat roof in the center of which was perched a little metal conning tower surmounted by a sending aerial. As Larry stood there, the broadcast magnified voice of a Robot droned out over the quiet city: "Trinight plus two hours. All is well." Strange mechanical voice with a formula half ancient, half super-modern! It was in this metal laboratory, Larry knew, that the other Time-traveling cage was located. And beneath it was the entrance to the great caverns where the Robots worked attending inert machinery to carry on the industry of this region. The night was very silent, but now Larry was conscious of a faraway throb--a humming, throbbing vibration from under the ground: the blended hum of a myriad muffled noises. Work was going on down there; manifold mechanical activities. All was mechanical: while the humans who had devised the mechanisms slept under the trees in the moonlight of the surface city. * * * * *