Page:The fairy tales of science.djvu/65

 Such a substance is potassium, the lightest of our metals. When exposed to the air potassium rapidly loses its metallic character by combining with oxygen, with which gas it forms potash; we therefore conclude that potassium has a strong affinity for oxygen.

If we throw a small fragment of this metal into water, it takes fire and burns, while swimming about on the surface of the liquid, with a brilliant light of a violet-red colour. When the combustion is over, no vestige of the potassium remains, but we find that the water has acquired the acrid taste of potash. The chemist thus interprets the phenomenon:—Water is a compound of oxygen and a highly inflammable gas called hydrogen; when potassium is thrown into Water it combines with a portion of its oxygen to form potash, and the heat which attends their union sets fire to the liberated hydrogen. It is not the metal that burns so furiously, but one of the constituents of water.

Here is a revelation far more wonderful than anything we find in our old story books!

Oxygen gas is the great supporter of combustion; even the metals will burn away in it like tinder. Hydrogen is the lightest gas known; it is very inflammable, and gives out an intense heat while burning. Water, the great antagonist of Fire, is built up of these two fiery elements!

Wherever we find Water we may be sure that these two elements are present. We may detect