which, though built on a much smaller scale, was not too different in
general outline from this one. The idea was worth investigation.

The doorway, which had afforded him a shelter from which to spy out
the land, yielded to his push, and he went through three large rooms
on the ground floor, paying no attention to the strange groups of
furnishings, but seeking something else, which he had luck to find in
the last room, a ramp leading down.

It was in the underground that he made his first important find. They
had seen ground vehicles in the city, a few still in operation, but
Raf had gathered that the fuel and extra parts for the machines were
now so scarce that they were only used in emergencies. Here, however,
was a means of transportation quite different, a tunnel through which
ran a ribbon of belt, wide enough to accommodate three or four
passengers at once. It did not move, but when Raf dared to step out
upon its surface, it swung under his weight. Since it ran in the
general direction of the Center he decided to use it. It trembled
under his tread, but he found that he could run along it making no
sound.

The tunnel was not in darkness, for square plates set in the roof gave
a diffused violet light. However, not too far ahead, the light was
brighter, and it came from one side, not the roof. Another station on
this abandoned way? The pilot approached it with caution. If his bump
of direction was not altogether off, this must be either below the
Center or very close to it.

The second station proved to be a junction where more than one of the
elastic paths met. Though he crouched to listen for a long moment
before venturing out into that open space, he could hear or see
nothing which suggested that the aliens ever came down now to these
levels.

They had provided an upward ramp, and Raf climbed it, only to meet his
first defeat at its top. For here was no opening to admit him to the
ground floor of what he hoped was the Center. Baffled by the smooth
surface over which he vainly ran his hands seeking for some clue to
the door, he decided that the aliens had, for some purpose of their
own, walled off the lower regions. Discouraged, he returned to the
junction level. But he was not content to surrender his plans so
easily. Slowly he made a circuit of the platform, examining the walls
and celling. He found an air shaft, a wide opening striking up into
the heart of the building above.

It was covered with a gril