3rdly—It is less heated by reflection.
Q. Why is air colder on a mountain “because it is less compressed?”
A. As the air in a valley is more compressed (by the mass of air above) than that on the top of a mountain, therefore more heat runs out; just as more water runs from a sponge, the closer it is squeezed together.
Q. Why is a mountain-top colder than a valley, “because the air there is more rarefied?”
A. As the air is more rarefied, its heat is diffused over a larger space and is less intense; just as a candle would show less light in a large room, than in a small one.
Q. Why is a mountain-top colder than a valley, “because the air there is less heated by reflection?”
A. Air is not heated by the sun, but by reflection from the surface of the earth; and as there is no earth round a mountain-top to reflect heat, therefore the air there is intensely cold.
Q. Why does rubbing our hands and faces make them feel warm?
A. Chiefly because the friction excites the latent heat of our hands and faces, and makes it sensible to our feeling.