etal stool at Tina, who was
trying to throw something at him. Then, turning, he sprang through the
open window casement and disappeared.

* * * * *

It was twenty feet down to the roof. We reached the window to see Tugh
picking himself up unhurt. Then, with his awkward gait but at amazing
speed, he ran across the roof to a small entrance in the face of the
dam where an interior staircase gave access to the roadway on top.

He was escaping us. The electrical gate was open to him. It was only a
few hundred feet along the dam roadway to that gate; and beyond it the
roadway was open into the city, where now we could see the distant
flashing lights of the Robots advancing along the dam.

Larry and I would have rushed to the roof to follow Tugh, but Tina
checked us. She said:

"No--he has too great a start. He's on top by now, and it's only a
short distance to the gate. There's a better way here: I can electrify
the gate again--trap him inside."[5]

[Footnote 5: There was a similar gate and wall-barrier at the Jersey
entrance to the dam, and both gates operated together. The nearby
Jersey section was, is still, an agricultural district save for a few
landing stages for the great airliners. The robots had spread into
Jersey; but since few humans were there, with only Robot
agriculturists working the section, the unimportant Jersey events have
not figured in my narrative.]

Tina found the gate controls. But they would not operate!

Those precious lost seconds, with Tugh running along the top of the
dam and his Robots advancing to join him!

"Tina, hurry!" I cried. Larry and I bent anxiously over her, but the
levers meant nothing to us. There were lost seconds while she
desperately fumbled, and Larry pleaded:

"Tina, dear, what's the matter?"

"He must have ripped out a wire to make sure of getting away. I--I
must find it. Everything seems all right."

A minute gone. Surely Tugh would have reached the gate by now. Or,
worse, the Robots would have come through, and would assail us here.

"Tina!" pleaded Larry, "don't get excited. Take it calmly: you can
find the trouble."

* * * * *

I rushed to the window. I could see the upper half of the cross wall
gate-barrier. It jutted above the top edge of the dam from the point
of vision. On the Manhattan side I saw the oncoming Robot lights. And
then suddenly I made out a light on this side of the barrier; i