turned to vapour in the outer layers
of the atmosphere. Here is a new danger for the high-altitude man, for
two others passed me when I was nearing the forty-thousand-foot mark.
I cannot doubt that at the edge of the earth's envelope the risk would
be a very real one.

"My barograph needle marked forty-one thousand three hundred when I
became aware that I could go no farther. Physically, the strain was
not as yet greater than I could bear but my machine had reached its
limit. The attenuated air gave no firm support to the wings, and the
least tilt developed into side-slip, while she seemed sluggish on her
controls. Possibly, had the engine been at its best, another thousand
feet might have been within our capacity, but it was still misfiring,
and two out of the ten cylinders appeared to be out of action. If I
had not already reached the zone for which I was searching then I
should never see it upon this journey. But was it not possible that I
had attained it? Soaring in circles like a monstrous hawk upon the
forty-thousand-foot level I let the monoplane guide herself, and with
my Mannheim glass I made a careful observation of my surroundings. The
heavens were perfectly clear; there was no indication of those dangers
which I had imagined.

"I have said that I was soaring in circles. It struck me suddenly that
I would do well to take a wider sweep and open up a new airtract. If
the hunter entered an earth-jungle he would drive through it if he
wished to find his game. My reasoning had led me to believe that the
air-jungle which I had imagined lay somewhere over Wiltshire. This
should be to the south and west of me. I took my bearings from the
sun, for the compass was hopeless and no trace of earth was to be
seen--nothing but the distant, silver cloud-plain. However, I got my
direction as best I might and kept her head straight to the mark. I
reckoned that my petrol supply would not last for more than another
hour or so, but I could afford to use it to the last drop, since a
single magnificent vol-plane could at any time take me to the earth.

"Suddenly I was aware of something new. The air in front of me had
lost its crystal clearness. It was full of long, ragged wisps of
something which I can only compare to very fine cigarette smoke. It
hung about in wreaths and coils, turning and twisting slowly in the
sunlight. As the monoplane shot through it, I was aware of a faint
taste of oil upon my lips, and