g and involved integrals and
equations upon the calculator.

The older man studied the broad back of the younger, bent over his
computations, and a tender, almost fatherly smile came over his careworn
face as he replied:

"Early? You? Just like you always were--plus fifteen seconds on the
deadline. The final dope is due right now." He plugged the automatic
recorder and speaker into a circuit marked "Observatory," waited until
a tiny light above the plug flashed green, and spoke.

"IPV _Arcturus_; Breckenridge, Chief Pilot; trip number forty-three
twenty-nine. Ready for final supplementary route and flight data, Tellus
to Mars."

"Meteoric swarms still too numerous for safe travel along the scheduled
route," came promptly from the speaker. "You must stay further away from
the plane of the ecliptic. The ether will be clear for you along route
E2-P6-W41-K3-R19-S7-M14. You will hold a constant acceleration of 981.27
centimeters between initial and final check stations. Your take-off
will be practically unobstructed, but you will have to use the utmost
caution in landing upon Mars, because in order to avoid a weightless
detour and a loss of thirty-one minutes, you must pass very close
to both the Martian satellites. To do so safely you must pass the
last meteorological station, M14, on schedule time plus or minus five
seconds, at scheduled velocity plus or minus ten meters, with exactly
the given negative acceleration of 981.27 centimeters, and exactly upon
the pilot ray M14 will have set for you."

"All x." Breckenridge studied his triplex chronometer intently, then
unplugged and glanced around the control room, in various parts of which
half a dozen assistants were loafing at their stations.

"Control and power check-out--Hipe!" he barked. "Driving converters and
projectors!"

The first assistant scanned his meters narrowly as he swung a
multi-point switch in a flashing arc. "Converter efficiency 100,
projector reactivity 100; on each of numbers one to forty-five
inclusive. All x."

"Dirigible projectors!"

* * * * *

Two more gleaming switches leaped from point to point. "Converter
efficiency 100, projector reactivity 100, dirigibility 100, on each of
numbers one to thirty-two, inclusive, of upper band; and numbers one to
thirty-two, inclusive, of lower band. All x."

"Gyroscopes!"

"35,000. Drivers in equilibrium at ten degrees plus. All x."

"Upper lights and lookout plat