ned, "I was only looking at the polar bear. Are polar
bears always white? Are--"

"You'd better take him away, sir," interrupted the sergeant. "He was
trying to pry out one of the bear's eyes with the stick of the
lollypop I give him. Take him."

The old gentleman extended both hands. His left found a grip in his
grandson's coat collar; his right, partly concealing a government
engraving, met the guard's with a clasp of gratitude.

"Sergeant," he remarked in a voice tense with feeling, "a half-hour
ago I expressed some ridiculous regrets that Drayle's invention had
been kept from the world. Now I realize its horrid menace. I shudder
to think it might have been responsible for two like him!"

The object of disapproval was shaken indicatively.

"Guard the secret well, Sergeant! Guard it well! The world's peace
depends upon you!" The old gentleman's words trembled with conviction.

Then alternately shaking his head and his grandson he marched down the
hallway, ebony cane tapping angrily upon the stone.

As the exhausted but happy warrior retraced his steps a high-pitched
voice floated after him.

"Grandpa, are polar bears _always_ white?"

* * * * *

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The Reader's Corner

_A Meeting Place for Readers of_

Astounding Stories

[Illustration: _The Reader's Corner_]

_The Invisible X-Flyers_

The following is a semi-technical description of the
operation of the invisible X-flyers used in "Jetta of the
Lowlands" as compiled by Philip Grant in the year 2021 from
official records of the Anti-War Department of the United
States of North America, and discovered recently by Ray
Cummings.

The attainment of mechanical invisibility reached a state of
perfection in the year 2000 sufficient to make it practical
for many uses. For a century this result had been sought. It
came, about the year 2000, not as a single startling
discovery, but as the culmination of the patient labor of
many men during many years. The popular mind has always
considered that science advances by a series of "great
scientific discoveries"; "unprecedented"; "revolutionary."
That is not so. Each step in the progress of scientific
achievement is built most carefully upon the one beneath it.
And generally the "revolutionary, unprecedented discovery"
has very little of itself that is new; rather it i