171. Why is a still summer air said to be sultry?
Because, being heated by the sun's rays, and being a bad conductor, it does not relieve the body by carrying off its heat.
172. Why does fanning the face make it feel cooler?
Because, by inducing currents of air to pass over the face, a part of the excessive heat is taken up and carried away.
173. Why does perspiration cool the body?
Because it takes up a part of the heat, and, evaporating, carries it into the air.
174. Why does blowing upon hot tea cool it?
Because it directs currents of air over the surface of the tea, and these currents take up a part of the heat and bear it away.
175. Why does air in motion feel cooler than air that is still?
Because each wave of air carries away a certain portion of heat and being followed by another portion of air, a further amount of heat is borne away.