Q. Why are France and Germany warmer now, than when the vine would not ripen there?
A. Chiefly because their vast forests have been cut down; and the soil is better drained and cultivated.
Q. What becomes of the water of ponds and tubs in summer-time?
A. Ponds and tubs in summer-time are often left dry, because their water is evaporated by the air.
Q. How is this evaporation produced and carried on?
A. The air contains heat, and changes the surface of the water into vapour; this vapour (blending with the air) is soon wafted away; while fresh portions of air blow over the water, and produce a similar evaporation; till the pond or tub is left quite dry.
Q. Why are the wheels of some machines kept constantly wet with water?
A. To carry off the heat (arising from the rapid motion of the wheels) by evaporation, as soon as it is developed.
Q. Why is mould hardened by the sun?