e poles there is no vegetation, not because of the
cold winter, but because of the hot summer. The winter winds
frequently blow over dead trees and roll them as far as the equatorial
seas. Other dead vegetation, because of the highly silicious water,
always gets petrified unless it is eaten first. What with the
quartz-speckled hides of the living vegetation and the solid quartz of
the dead, a forest is spectacular.

The silicone animals live on the plants. They chew them up, dehydrate
them, and convert their silicious outer bark and carbonaceous
interiors into silicones for themselves. When silicone tissue is
metabolized, the carbon and hydrogen go to CO_{2} and H_{2}O, which
are breathed out, while the silicone goes into SiO_{2}, which is
deposited as more teeth and armor. (Compare the terrestrial octopus,
which makes armor-plating out of calcium urate instead of excreting
urea or uric acid.) The animals can, of course, eat each other too, or
make a meal of the small carbonaceous animals of the equatorial seas.

Further note that the animals cannot digest plants when they are cold.
They can eat them and store them, but the disposal of the solid water
and CO_{2} is too difficult a problem. When they warm up, the water in
the plants melts and can be disposed of, and things are simpler.

II

THE FLUORINE PLANET

1. THE STAR AND PLANET

The planet named Niflheim is the fourth planet of Nu Puppis, right
angle 6:36, declension-43:09; B8 type star, blue-white and hot, 148
light years distant from Earth, which will require a speed in excess
of light to reach it.

Niflheim is 462,000,000 miles from its primary, a little less than the
distance of Jupiter from our sun. It thus does not receive too great a
total amount of energy, but what it does receive is of high potential,
a large fraction of it being in the ultra-violet and higher
frequencies. (Watch out for really super-special sunburn, etc., on
unwarned personnel.)

The gravity of Niflheim is approximately 1 g, the atmospheric pressure
approximately 1 atmosphere, and the average ambient temperature
about-60 deg.C;-76 deg.F.

2. ATMOSPHERE

The oxidizer in the atmosphere is free fluorine (F_{2}) in a rather
low concentration, about 4 or 5 percent. With it appears a mad
collection of gases. There are a few inert diluents, such as N_{2}
(nitrogen), argon, helium, neon, etc., but the major fraction consists
of CF_{4} (carbon tetrafluoride), BF_{3} (boron