Note 19 — Chapter XXV · CHEMISTRY WITHOUT A LABORATORY.
Reading edition
It is the same with a number of other common products, such as clay, sandstone, etc., the composition of which chemistry has revealed. Argil, or clay, slate, and schist all contain a metal—aluminium, which has become most valuable for industrial purposes. Stones for building are composed of a metal combined with carbon and oxygen—calcium; sandstone is composed of silicium, a metallic body united with oxygen; and sulphate of magnesia, which enters into the composition of a purgative drink, also contains a metal—magnesium.