to get well."

"I have some more of those crystals dissected out, Doctor."

"Keep them in the dark until Mr. Davis comes after them. I want to
take a few of them back to Washington for study."

"You expect another attack to-night, Doctor?"

"Yes, sometime after sundown."

"What, in heaven's name, is it?"

"Heaven has nothing to do with it, Captain; the stuff comes from the
devil's regions and it is the product of a Russian chemist, who I
sometimes believe is verily the devil himself. How it's done and what
it is, I haven't found out yet, but I am going to investigate a little
to-night. The effect is what you have seen. Are you familiar with the
various forms of oxygen?"

"The forms of oxygen? Why, there is only one, oxygen gas. Wait a
minute though, there is another form, ozone. Are there any more?"

"None that have been previously listed and studied, but at least one
other form exists. Those crystals are pure oxygen."

"Impossible! Oxygen is a gas at all ordinary temperatures."

* * * * *

"Yes, a gas, but one whose density varies. Oxygen, to which we
chemists assign the formula O_{2}, meaning that its molecule consists
of two atoms of oxygen, has a weight of 32 grams per gram molecule.
Ozone, to which we assign the formula O_{3}, meaning that its molecule
contains three atoms of oxygen, weighs fifty per cent more or 48 grams
per gram molecule. This new form has a density less than water, but
tremendously greater than any known gas. I have not yet been able to
determine its structure, so I will have to assign to it the formula,
O_{x}, meaning an indefinite number of atoms per molecule. The only
name which suggests itself is oxyzone, a combination of oxygen and
ozone.

"The stuff is a polymerization, or condensation, to speak roughly, of
the oxygen of the air. The oxygen takes this form which the lungs
cannot assimilate except with great difficulty and with great damage
to the tissues. The oxyzone will break down rapidly under the
influence of sunlight or of any ray whose wave-length is shorter than
indigo. As a result, it disappears as soon as the sun is up and it
will reappear after dark. That is why I suggested X-rays as a
treatment. They have a very short wave-length and will penetrate
tissues and affect the particles in the lungs themselves. Once the
material is removed from the lungs, the cauterization of the tissue
ceases and it is merely a matter of slow recovery."