149. Why are woollen fabrics bad conductors of heat?
Because there is a considerable amount of air occupying the spaces of the texture.
150. Is air a good or a bad conductor?
Air is a bad conductor, and it chiefly transmits heat, as water does, by convection.
151. Is water a good or a bad conductor?
Water is an indifferent conductor, but it is a better conductor than air.
152. Why, when we place our hands in water, which may be of the same temperature as the air, does the water feel some degrees colder?
Because water, being a better conductor than air, takes up the warmth of the hand more rapidly.
153. Why, when we take our hands out of water do they feel warmer?
Because the air does not abstract the heat of the hand so rapidly as the water did, and the change in the degree of rapidity with which the heat is abstracted produces a sensation of increased warmth.