All metals do not conduct heat at the same rate as may be proved by holding in the flame of a candle at the same time a piece of silver wire and a piece of platina wire, when the silver wire will become too hot to hold, much sooner than the platina. Or cut a cone of each wire, tip it with wax, and place it upon a heated plate (as a fire-shovel), when the wax will melt at different periods.