A Catechism of Familiar Things; Their History, and the Events Which Led to Their Discovery.

by Benziger Brothers.

PREFACE.

This book, a reprint of a successful English publication, has been so enlarged as to be to all intents and purposes new. It has been carefully revised by a Reverend gentleman, who for some time filled the chair of Physics and Chemistry in one of our colleges.

Recent inventions and improvements are described in a simple, popular style, so as to be easily understood by all, and short notices are given of prominent inventors and scientists. The paragraphs relating to doctrinal matters conform in every respect to the teachings of the Church.

A feature which will commend the book to every teacher is the definitions of difficult words and terms, following the paragraphs in which such words occur.

Technical language is avoided as much as possible, so as to enable young pupils to become familiarly acquainted with the various phenomena of nature, the leading characteristics and general history of the objects of the animal, vegetable, and mineral kingdoms, and the fundamental truths of the arts and sciences.

The ill.u.s.trations are of a superior order, and a very complete Index, which will be appreciated by every teacher, supplements the book. In a word, no pains have been spared to enhance the value of the work, and render it an important auxiliary in the dissemination of useful and entertaining knowledge.

The publishers beg to acknowledge their obligations to the Sisters of Mercy, Loretto, Pa., to whose kindness they are indebted for many valuable suggestions.

In the hope that the book may be found suited to the accomplishment of its aim, it is respectfully submitted to schools and instructors of youth, who are the best judges of its merits.

CHAPTER I.

DEW, WATER, RAIN, SNOW, HAIL, ATMOSPHERE, WIND, LIGHTNING, THUNDER, ELECTRICITY, TWILIGHT, AND THE AURORA BOREALIS.

What is Dew?

Moisture collected from the atmosphere by the action of cold. During the day, the powerful heat of the sun causes to arise from the earth and water a moist vapor, which, after the sun sinks below the horizon, is condensed by the cold, and falls in the form of dew. Dews are more copious in the Spring and Autumn than at any other season; in warm countries than in cold ones: because of the sudden changes of temperature. Egypt abounds in dews all the summer; for the air being too hot to condense the vapors in the day-time, they never gather into clouds and form rain.

_Horizon_, the line which bounds the view on all sides, so that the earth and sky appear to meet. A Greek word, from the verb signifying to mark boundaries.

_Temperature_, degree of heat or cold.

_Condense_, to cause the particles of a body to approach or unite more closely.

What are its uses?

It cools and refreshes the vegetable creation, and prevents it from being destroyed by the heat of the sun. All hot countries where there is little or no rain are therefore blessed with this provision by the all-bountiful Creator, to render them luxuriant and inhabitable; and the dews which fall are so copious, that the earth is as deeply soaked with them during the night as if a heavy rain had fallen. For this reason also it is, that we so often read in the Bible of the "dew of Heaven" being promised to the Israelites as a signal favor.

_Luxuriant_, fertile, flourishing.

_Signal_, remarkable, eminent.

From what does the vapor originate?

Vapor is water, combined with a still greater quant.i.ty of caloric,--that is, an imponderable and subtile form of matter, which causes the sensation of heat; and which, driving asunder the particles of the water, renders it aeriform.

_Imponderable_, without sensible weight.

_Subtile_, thin, not dense, or compact.

_Particle_, a small portion of matter.

_Aeriform_, having the form of air.

What is Water?

The fluid which covers more than three-fifths of the surface of our globe, and which is necessary for the life and health of the animal and vegetable creation; for without water there would be neither rain nor dew, and everything would perish. It is likewise a necessary beverage for man and the inferior animals.

_Beverage_, drink, liquor for drinking.

In how many states do we find Water?

In four: 1st, solid, as in ice, snow, hail, &c.; 2d, fluid, as in its common form; 3d, aeriform, as in steam; and 4th, in a state of union with other matter. Its most simple state is that of ice, which is water deprived of a certain portion of its caloric: crystallization then takes place, and the water becomes solid and is called ice.

_Crystallization_, the process by which the parts of a solid body, separated by solution or fusion, are again brought into the solid form. If the process is slow, the figure a.s.sumed is regular and bounded by plane and smooth surfaces.

_Solution_, the diffusion of a solid through some liquid.

_Fusion_, melting, or rendering fluid by heat.

From what cause is the Water deprived of its caloric?

From the coldness of the atmosphere: underneath the poles of our globe it is mostly solid; there it is similar to the hardest rocks, and may be cut with a chisel, like stone or marble. This great solidity is occasioned by the low temperature of the surrounding air; and in very cold countries ice may be ground so fine as to be blown away by the wind, and will still be ice.

_Poles_, the extremities or ends of the axis, an imaginary line, supposed to be drawn through the centre of the earth; or when applied to the heavens, the two points directly over them.

Is ice the only instance of Water existing in a state of solidity?

No; it is found in a solid state in many minerals, as in marble, &c., and is then called _water of Crystallization_. It is essential, in many cases, to their solidity and transparency.

_Essential_, necessary.

_Transparency_, clearness, the power of transmitting light.

Does Nature decompose Water in any of her operations?

Yes: every living vegetable has the power of decomposing water, by a secret process peculiar to itself. Fish, too, and all cold-blooded amphibious animals are gifted with the same power.

_Decomposing_, separating a mixed body into its several parts.