in actual contact, so the repulsive power is greater before contact.]

[_The blue mist_. l. 20. Mists are clouds resting on the ground, they
generally come on at the beginning of night, and either fill the moist
vallies, or hang on the summits of hills, according to the degree of
moisture previously dissolved, and the eduction of heat from them. The
air over rivers during the warmth of the day suspends much moisture, and
as the changeful surface of rivers occasions them to cool sooner than
the land at the approach of evening, mists are most frequently seen to
begin over rivers, and to spread themselves over moist grounds, and fill
the vallies, while the mists on the tops of mountains are more properly
clouds, condensed by the coldness of their situation.

On ascending up the side of a hill from a misty valley, I have observed
a beautiful coloured halo round the moon when a certain thickness of
mist was over me, which ceased to be visible as soon as I emerged out of
it; and well remember admiring with other spectators the shadow of the
three spires of the cathedral church at Lichfield, the moon rising
behind it, apparently broken off, and lying distinctly over our heads as
if horizontally on the surface of the mist, which arose about as high as
the roof of the church. There are some curious remarks on shadows or
reflexions seen on the surface of mists from high mountains in Ulloa's
Voyages. The dry mist of summer 1783, was probably occasioned by
volcanic eruption, as mentioned in note on Chunda, Vol. II. and
therefore more like the atmosphere of smoke which hangs on still days
over great cities.

There is a dry mist, or rather a diminished transparence of the air,
which according to Mr. Saussure accompanies fair weather, while great
transparence of air indicates rain. Thus when large rivers two miles