A Catechism of Familiar Things Part 38

_Chemist_, one who understands the science of chemistry.

Of which of these Simple or Primitive Earths are the solid portions of the globe princ.i.p.ally 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 gla.s.s. It is the princ.i.p.al ingredient of most of the precious stones.

What are the chief uses of Silex?

It is the most durable article for the formation of roads; a necessary ingredient in earthenware, porcelain, and cements; and the princ.i.p.al material of gla.s.s and vitreous substances. The making of pastes or artificial gems is a branch of the art of gla.s.s-making; the basis used is a very hard and pure silex.

_Basis_, that part of any mixture which is the ground or base; the first principle or element of a substance.

Describe the properties of Lime.

It is of a white color, and possesses a hot, caustic taste. It forms peculiar salts with acids; changes vegetable blues to green; will not fuse; gives out a quant.i.ty of caloric when united with water; and absorbs carbonic acid when exposed to air. Lime is very useful in the arts and manufactures, in medicine, &c. The farmers use it as manure to fertilize land.

_Caustic_, burning, corroding: a term applied to substances which eat away and burn any thing with which they are brought in contact.

In what state is Lime found in nature?

Never native, but combined with other substances;--generally with an acid, and most plentifully with carbonic acid, as in chalk, marble, &c. It is also found in vegetables, and is the basis of animal bones; it likewise occurs in the water of the ocean, and in that of all springs and rivers. The method of procuring _lime_, from chalk, marble, limestone, oyster-sh.e.l.ls, &c., has already been described in a former chapter.

What are the properties of Clay?

Argil, or pure clay, also called _alumina_, from its being the basis of alum, is soft to the touch, adhesive, and emits a peculiar odor when moistened;--forms a paste with water, and hardens in the fire.

Its uses are so various and important, that it would have been almost impossible for man to have attained his present degree of civilization, if it had not been given him by nature in such abundance. Its uses have already been described in the arts of brick-making, pottery, &c. Besides these three princ.i.p.al primitive earths just described, there are seven others, having several properties in common, yet each possessing its different and specific properties, and evidently designed by nature for different purposes of utility.

_Specific_, belonging to its particular species.

_Utility_, usefulness.

What is a Volcano?

An opening in the surface of the earth, or in a mountain, from which are ejected smoke, flames, stones, lava, &c. Beneath the outer crust of the earth inflammable materials appear to exist, which different causes excite into combustion. Volcanoes are supposed to owe their origin to the metals and minerals which form the basis of earths and alkalies; and which, when ignited, expand,--shake the rocky foundations,--and sometimes, bursting through, produce all the destructive effects of earthquakes. They break forth under the sea, as well as the land, and throw up mountains which rise above the level of the water. During an eruption of Vesuvius, A.D. 79, three cities, Herculaneum, Pompeii, and Stabiae, were overwhelmed, and lay buried beneath the matter ejected from the volcano until within a few years, when excavations were made and many relics discovered;--streets, houses, papyri, (ma.n.u.scripts,) grain, fruit, bread, medicines, &c.

&c., all in a remarkable state of preservation, have been found just as they were left by the terrified inhabitants at the time of the eruption!

_Eruption_, an issuing or breaking forth with violence.

_Ejected_, thrown out.

Are there many Volcanoes?

There are upwards of two hundred volcanoes upon the globe; more than one half of them are in America and Oceanica The most noted volcanoes in America are Cotopaxi (the highest in the world), near Quito; Popocatapetl, in Mexico; Cosiguina, and the Water Volcano, in Guatemala. In France, Spain, Portugal, and many other countries, there are districts which show the former existence of volcanoes, which have long been extinct; near Naples, in an area of two hundred square miles, there are sixty craters, some of them larger than Vesuvius; in one of these, the town of c.u.mea has stood for three thousand years.

What can you say of new islands formed by Volcanic Agency?

Many examples of new islands rising out of the sea by volcanic action are on record. Some of them are permanent, but others, after a time, disappear. Teneriffe, Iceland, Sicily, St. Helena; part of Sumatra, Java, j.a.pan; and the Sandwich Islands, seem to have been upheaved by volcanic agency; Hawaii, the largest of the last-named group, contains an area of four thousand square miles, and rises eighteen thousand feet above the ocean.

What are Earthquakes?

Shakings or vibrations of the ground; sometimes accompanied by rents, and rockings or heavings of the surface, so as to overthrow buildings, and swallow up towns and large tracts of country. They are attended with a terrible subterranean noise, like thunder, and sometimes with an eruption of fire or water, or else of smoke or winds.

_Subterranean_, underground.

What is supposed to cause them?

An electrical action between the atmosphere and some deep sub-strata; or the sudden formation of gaseous matter beneath the surface of the earth by internal volcanic fires. Many hot countries, where much electrical disturbance takes place, are very subject to them: earthquakes almost always precede volcanic eruptions; an open volcano, also, probably diminishes the force of earthquakes, by the vent which it affords. Earthquakes, at different times, have been productive of the most terrific effects: towns and cities have been swallowed up, and thousands of people destroyed by them. The island of Jamaica is remarkable for the earthquakes which frequently happen there.

_Precede_, to go before.

_Vent_, opening.

_Terrific_, full of terror, dreadful.

Where is Jamaica situated?

In the West Indies,--a large group of fertile islands which lie between North and South America. Jamaica is the princ.i.p.al one of those which belong to the English.

CHAPTER XVII.

ARCHITECTURE, SCULPTURE, USE OF MONEY, NAVIGATION.

What is meant by Architecture?

The art of building or erecting edifices fit for the habitation of man, to defend him from the weather, and for his domestic comfort and convenience; for devotion, trade, and other purposes, and for the use of civilized life in every capacity.

_Capacity_, state, condition.

Is not this an art of great antiquity?