r were driving against a canvas moving in a slight
breeze--canvas light and loose enough to be held in place by the
resistance of the air so as to enclose him. Or maybe I should say
"veiling" instead of canvas--or something still lighter and airier.
Have you ever seen milk poured carefully down the side of a glass vessel
filled with water? Well, clear air and fog seemed to behave towards
each other pretty much the same way as milk in that case behaves towards
water.

I am rather emphatic about this because I have made a study of just such
mists on a very much smaller scale. In that northern country where my
wife taught her school and where I was to live for nearly two years as
a convalescent, the hollows of the ground on clear cold summer nights,
when the mercury dipped down close to the freezing point, would
sometimes fill with a white mist of extraordinary density. Occasionally
this mist would go on forming in higher and higher layers by
condensation; mostly however, it seemed rather to come from below.
But always, when it was really dense, there was a definite plane of
demarcation. In fact, that was the criterion by which I recognised this
peculiar mist. Mostly there is, even in the north, a layer of lesser
density over the pools, gradually shading off into the clear air above.
Nothing of what I am going to describe can be observed in that case.

One summer, when I was living not over two miles from the lakeshore, I
used to go down to these pools whenever they formed in the right way;
and when I approached them slowly and carefully, I could dip my hand
into the mist as into water, and I could feel the coolness of the
misty layers. It was not because my hand got moist, for it did not. No
evaporation was going on there, nor any condensation either. Nor did
noticeable bubbles form because there was no motion in the mass which
might have caused the infinitesimal droplets to collide and to coalesce
into something perceivable to my senses.

Once, of a full-moon night, I spent an hour getting into a pool like
that, and when I looked down at my feet, I could not see them. But after
I had been standing in it for a while, ten minutes maybe, a clear space
had formed around my body, and I could see the ground. The heat of my
body helped the air to redissolve the mist into steam. And as I watched,
I noticed that a current was set up. The mist was continually flowing
in towards my feet and legs where the body-heat was least. And