Some of the metals assume certain definite forms in return from the fluid to the solid state. Bismuth shows this property more readily than most others.

Experiment.

Melt a pound or two of bismuth in an iron ladle over the fire; remove it as soon as the whole is fluid; and when the surface has become solid break a hole in it and pour out the still fluid metal from the interior; what remains will exhibit beautifully formed crystals of a cubic shape.

Sulphur may be crystallized in the same manner, but its fumes, when heated, are so very unpleasant that few would wish to encounter them.

One of the most remarkable facts in chemistry—a science abounding in wonders—is the circumstance that the mere contact of hydrogen, the lightest body known, with the metal platinum, the heaviest when in a state of minute division called spongy platinum, produces an intense heat sufficient to inflame the hydrogen; of course this experiment must be made in the presence of atmospheric air or oxygen. If a small piece of the metal in the state above named be introduced into a mixture of oxygen and hydrogen, it will cause them to explode. A very small quantity of gas should be employed and placed in a jar lightly covered with a card, or the explosion would be dangerous.