A Catechism of Familiar Things; / Their History, and the Events Which Led to Their Discovery. / With a Short Explanation of Some of the Principal Natural Phenomena. For the Use of Schools and Families. Enlarged and Revised Edition.

by Anonymous

Crater, the mouth or opening of a volcano.

Petrified, hardened into stone.

You mentioned Silicious and Argillaceous Earths: is not, then, the earthy covering of our globe of one common character?

No; by earth is understood a combination of many distinct bodies. Chemists, by separating earths from each other, and from foreign matters connected with them, have discovered nine or ten primitive earths; all of these, except silex, are compounds of oxygen with metallic bases.

Chemist, one who understands the science of chemistry.

Of which of these Simple or Primitive Earths are the solid portions of the globe principally composed?

Of flint or silex, lime or calcareous earth, and clay or argil, in various degrees of combination, the greatest parts of the mountains and plains, and the whole of what we commonly understand by soil, mould, earth, &c. are composed. These, however, though forming nearly all of the solid portions of the world, are constantly mixed with foreign matters, as metals, (particularly iron,) and acids, (as carbonic acid.)

What are the properties of Silex?

Silex, or pure flint, will not dissolve in water, nor can it be melted by itself in any heat; but combined with alkalies, as soda or potash, it forms glass. It is the principal ingredient of most of the precious stones.