yawning gates where the track abruptly ended at the brow of the
Palisades--the empty chasm where, if all went right and no mistake
had been made in build, engine-power, or control, the initial leap of
_Nissr Arrib ela Sema_ was to be made.

Came a moment's wait. Faintly the pulsing of the engines trembled
the fabric of _Nissr_. Finely balanced as they were, they still
communicated some slight vibration to the ship. The Master snicked the
switch of the magnetic-anchor release; and now the last bond that held
_Nissr_ to her cradle was broken. As soon as the air-skid currents
should be set going, she would be ready for her flight.

This moment was not long in coming. Another turn of a switch, and all
at once, far below, a faint, continuous hissing made itself audible.
Compressed air, forced through thousands of holes at the bottom of the
floats, was interposing a gaseous cushion between those floats and the
track, just as it could do between them and the earth wherever _Nissr_
should alight.

Suspended thus on a thin layer of air, perhaps no more than a
sixteenth of an inch thick but infinitely less friction-producing than
the finest ball-bearing wheels and quite incapable of being broken,
the ship now waited only the application of the power in her vast
propellers.

"Let in numbers two and four," commanded the Master, suddenly, into
the engine-room telephone. "In five seconds after we start, hook up
one and three; and five later, the other two."

"Aye, aye, sir," came back the voice of Auchincloss, chief engineer.