Observe attentively the steam that escapes from the spout of a
tea-kettle, at the moment the water begins to boil, and you will
perceive the steam to be condensed in minute drops on the interior
edges of the spout. A few moments afterwards, provided the water
continue to boil, the spout of the kettle will become perfectly dry;
and, at the same time, close to it, there will be a certain space, say
from one-half to three-fourths of an inch, throughout which not a
particle of steam will be perceptible. This may be easily explained.
When the water in the kettle begins to boil, the spout being cooler
than the steam issuing from it, a portion of that steam is condensed.
As more steam escapes, the metal soon becomes as hot as the steam,
will no longer condense it, and the spout becomes dry. By this time
the steam will displace the air immediately opposite the orifice of
the spout, whence it will issue dry and invisible. As it is cooled
by mixing with the surrounding air, it assumes its well-known cloudy
appearance.
[Illustration]
[Illustration: FIRE, WATER, AND AIR.]
[Illustration]