The single concept of heat flow covered briefly by Balestrino (above) is further explicated here in a series of illustrated examples and one simple but telling experiment in which a child puts his left hand into hot water and his right into cold, then plunges both into a medium bowl: ""Can you guess why the water in the middle bowl feels different to each hand?"" Those who can't guess yet will surely understand before Mr. Froman is through; if they're alert Balestrino will take them farther, but Froman makes sure that no one is left behind.