Why does wrapping straw around a pump in winter, prevent the water in it from freezing?
Because the stalks of straw are hollow, and the air in the stalks makes them poor conductors of heat.
Will straw, wrapped around shrubbery, prevent it from freezing?
It will; because it keeps the heat of the shrubbery from passing off into the air.
Why are rooms warmer from having double windows?
Because the air which is confined between the double windows, being a poor conductor, keeps the warmth of the room from escaping.
Why is the space between the double walls of ice-coolers filled with charcoal?
Because charcoal is a poor conductor, and keeps the heat of the air from the ice.
Why do ice-houses have double walls, with saw-dust or straw between them?
Because the saw-dust and the straw are both poor conductors, and keep the heat of the air from the ice.