A. Three; by radiation, by conduction and by convection.
Q. If the fire consisted of glowing fuel, show how the heat enters the water and forms steam?
A. The heat from the glowing fuel passes by radiation through the air space above the fuel to the furnace crown. There it passes through the iron of the crown by conduction. There it warms the water resting on the crown, which then rises and parts with its heat to the colder water by conduction till the whole mass of water is heated. Then the heated water rises to the surface and parts with its steam, so a constant circulation of water is maintained by convection.
Q. What does water consist of?
A. Oxygen and hydrogen.
Q. In what proportion?
A. Eight of oxygen to one of hydrogen by weight.
Q. What are the different kinds of heat?
A. Latent heat, sensible heat and sometimes total heat.
Q. What is meant by latent heat?