First book of science, designed for public and private schools

Contents

FAGB

CHAPTER I. — Mechanical Properties of Bodies . 11 II. — Mechanics of Solids . 16

III. — Mechanics of Fluids . 59

IV. — Sound . 77

V. — Light . 90

VI. — Electricity . 116

VII. — Magnetism . 138

VIII. — Theoretical Astronomy . 153

IX. — Descriptive Astronomy . 175

Preface

The present little volume treats of the elements of Natural Science, and is designed to meet the wants of young persons, who do not intend to pursue a complete course of academical study.

The catechetical form has been adopted, as better adapted to class recitation, in the case of young pupils, than the ordinary didactic form, and as admitting of greater condensation. It has, also, the important advan¬ tage of permitting a more rigid adherence to a logical method in the treatment of topics, and thus securing greater distinctness of conception, and consecutiveness of thought, on the part of the pupil.

The mental culture to be derived from the exercise of framing answers to the questions put by the teacher, can be truly realized only by the more advanced student. The young beginner is seldom capable of making his answers sufficiently precise, nor will he readily acquire by practice alone the habit of accurate statement.

As in a book intended for the young no opportunity should be neglected of addressing the mind through the

VI

PREFACE.

eye, the principles stated are copiously illustrated by pictorial representations.

Especial pains are taken that clear conceptions should be obtained of the* fundamental principles of the differ¬ ent branches of Natural Science. With the view of accomplishing this object more effectually, the method is pursued of ascending from particulars to generals. Prac¬ tical applications of principles are added wherever they could be introduced to advantage.

Introduction

As a fitting introduction to the pleasant task that is before us, we will take a general survey of the ground to be passed over. On glancing hastily over it we might conjecture that the order of things in the realm of inanimate Nature was fixed and invariable ; but on a nearer view we perceive that all things, inanimate as well as animate, are subject to change. We soon discover, too, that change follows change in a certain established succession, and that a beautiful order and harmony everywhere prevail. We recognize the operation of natural causes as invariably producing certain effects, and so rise from the conception of that which is changeable and transient to that which is unalterable and everlasting. Looking farther, we discern the secret workings of the primary cause of this universal activity of change. We call it Force, and seem to see in it the subtile chain by which the universe is bound to the throne of the Creator. Our first great object, then, will be to inspect the characteristic forms which this primary principle of change as¬ sumes, or the so-called forces of nature, and examine into the effects they produce. While engaged in this interesting study we shall learn how these natural agents are made serviceable to man, and brought to labor obediently to his requirements.

After taking this comprehensive survey, we will descend to a lower point of view, and inquire into the various means by which external Nature produces impressions on our senses. When “ the Spirit of God moved upon the face of the waters,” and Force be¬ gan to execute its divine commission, to evoke order out of chaos, Light burst into existence, the first of all created things, proclaim¬ ing the ultimate design of creation. The Divine Power which created the universe has sustained it and will sustain it through all

Till

INTRODUCTION.

time, and the all-bounteous light, fulfilling its destiny, now gladdens the earth and its teeming world of life as with the smile of His be¬ neficence. It will be a pleasant task to follow the flashing light in its movements, study its deportment under different circumstances, and divine, if possible, by what subtile handicraft a beauteous dra¬ pery of many-colored light is daily fashioned and spread over the earth. It will be interesting, too, to scan the wonderful contriv¬ ances which the ingenuity of man has devised to increase his power of vision — the microscope, which discloses to view a new world of thronging life existing unheeded everywhere around us, and the telescope, which reveals the existence of innumerable shining worlds peopling the depths of immensity.

In the same connection the philosophy of sound will occupy our attention. We shall seek to understand its nature, the manner in which it is produced and conveyed to the ear, and the various ways in which it is modified in its character and affected iri its propaga¬ tion. The magical charm that dwells in the “ concord of sweet sounds” will yield up its secret to our scrutiny.

Changing again our point of view, and seeking for the physical actions which bodies may have on each other, a new avenue opens out before us, conducting into a region not yet fully explored, but which has already rewarded research with many wonderful curios¬ ities and valuable treasures. It is found that, besides light, and its ordinary attendant, Heat, other active principles, called Electricity and Magnetism, are intimately associated with the particles of bodies. In these ethereal principles, ever mysteriously at work in the most hidden recesses of nature, and coming forth at the call of science, are recognized but new forms of force, clothed with almost spiritual bodies.

Thus far our contemplations are mostly confined to the face of the earth. Looking away from the earth we see bending over us the blue dome of the sky, and admire its wondrous fretwork of stars. Observing attentively, it is perceived that the vaulted sky, with its luminous tracery, is not motionless and firmly estab¬ lished upon the broad pavement of the earth, but is in reality an ever-shifting panorama of celestial lights, gliding noiselessly over us. If we were to believe with the sages of the olden time, we might suppose a succession of crystalline spheres, freighted with stars, to be rolling around, and almost hear the music of their cease¬ less revolution. But this may not be in the present day; a Coperni¬ cus has lived in a previous age, at the wave of whose hand all the

INTRODUCTION.

IX complicated celestial apparatus of mail’s creation has passed away “like the baseless fabric of a vision.” We now look through the filmy blue veil of the atmosphere into the immeasurable depths of space, and wonder unceasingly at the glories which fill immensity. The imaginary foundations of the earth are broken up, and it comes forth arrayed in a garment of light, to take its olace among the rolling stars that circle around the sun. The system of the world has expanded into proportions that transcend our highest powers of con¬ ception ; but its strange complexity has dissolved into a divine sim¬ plicity. In its unrestrained flight through the fields of space, the mind seems almost to grasp the infinite, in extent and duration. Time past and time future swell into proportions before inconceiv¬ able. The vast cycles of change going on in the heavens seem, as it has been sublimely said, like the recurring beats of the pendulum of eternity. And so, too, by sounding the depths of space, from star to star, with the ethereal light for a sounding line, we almost measure off the infinity of distance. How greatly it tends also to enlarge our ideas of the past duration of the universe, to know that the light which comes from )7on star, struggling into view in the field of the telescope, is wearied with the flight of tens of thousands of years.

If it should be imagined that the earth, if a shining star, bears about it no indications of a past existence, immeasurable by the flight of years, the geologist will tell us that the records of such an existence are found inscribed by the hand of time, or rather the finger of God, upon tables of stone buried beneath its surface. Passing over their upturned edges, he unfolds these tablets one after another, and reads the history of the earth as there traced in unfading characters. There is found, too, in the very structure and constitution of the rocky framework of the earth undoubted traces of a primeval age, when the mountains, and even the whole earth, were melted with fervent heat, and the flames played with their forked tongues over the wide regions that are now glowing with beauty and teeming with a bounteous life. This fiery conflict was in fact the process by which the materials for the things of life that were to spring up from the earth were prepared. Countless ages passed away, the flickering flames died out, and the earth lost its vesture of fire. Another succession of ages rolled by, and the up¬ lifted mountains began to show their tops above a waste of waters, and dot its wide expanse with islands. These rose and sank, and one wave of revolution after another swept over the face of the

1*

X

INTRODUCTION.

earth, until at last the continents stood firm, and the sea was shut up within its bounds. Successive worlds of animal and vegetable life came and passed away, keeping pace with the changes that oc¬ curred in the material world, until man appeared as the “ lord of creation” and the consummation of the Divine plan.

These teachings of the book of Nature in regard to the great antiquity of the earth and the material universe, are now well un¬ derstood to be in harmony with the Mosaic account of creation. The volume of Creation and the Bible, two books of revelation from the same Divine Author, can not but confirm and illustrate each other when rightly understood,

Should it be supposed by the reader that such studies, how¬ ever interesting or ennobling they may be, can have but little prac¬ tical utility, we would remind him of the time-honored maxim, that “ Science is the handmaid of Art.” In fact, Science has responded to the demands of Art, and attended upon its progress in all the past. As new discoveries in science have been made, new indus¬ trial arts have sprung up. The most insignificant scientific truths have thus proved to be treasures of incalculable value to mankind. Nor have those truths which seemed to be too exalted ever to wear the homely garb of working-day life, failed to do good service in be¬ half of the material interests of mankind. The shining orbs that move so far above us, are lights in the firmament “ for signs and for seasons, and for days and for years ;” and white-winged commerce bears its treasures across the sea under the guidance of the remote stars. Science has given to the iron-horse his breath of fire and sinews of strength — disarmed the lightning of its terrors, and com¬ pelled it to wait upon man as his swift-winged messenger. Science has taught the sun-beam to daguerreotype the “ human face divine.” Science invents machinery, contrives articles of convenience and luxury, and in a thousand ways cheers and adorns the pathway of our daily life.

FIRST BOOK

OF

NATURAL PHILOSOPHY AND ASTRONOMY.

CHAPTER I.

MECHANICAL PROPERTIES OF BODIES.

1. Is a piece of wood, or a pebble, or an iron bar, all solid mat¬ ter?

It is part matter and part empty space.

2. Is there as much matter in a piece of wood as in an iron bar of the same size ?

There is less matter and more empty space in the wood than in the iron.

3. How is this fact generally expressed ?

It is said that iron is denser , or more compact, than wood.

4. What are the empty spaces in the interior of bodies called?

Pores. The pores are visible in many substances ; for example, in sponge, cork, and some kinds of wood.

NATURAL PHILOSOPHY.

5. Are the pores in the interior of bodies entirely devoid of matter of any kind ?

The larger visible pores contain air; and the more mi¬ nute pores, in even the densest substances, contain a very subtile ether, which also fills all space.

6. Can a body of matter be divided into smaller and smaller parts without any apparent limit?

It can.

7. What are the two ways in which matter can be divided and subdivided ?

Mechanically , that is, by pounding, grinding, etc. ; and by solution .

8. Give an example of the minute subdivision of matter by solution.

A grain of blue vitriol, smaller than the smallest pea,

will give a blue tinge to half a gallon of water containing 20 drops of spirits of hartshorn. In this half gallon there are 250,000 drops.

9. Are there any last particles that can not be divided any further ?

Chemistry informs us that there are

10. What are these indivisible particles called?

Atoms. Every body of matter is made up of indivisible atoms.

1 1 . Are these atoms so close together as to be in actual contact ?

They are not, they always stand apart from each other.

12. What holds them together?

Each particle pulls the others toward it, or attracts them, just as a magnet attracts a piece of iron that is brought near it.

MECHANICAL PROPERTIES OF BODIES.

13. What is this attraction between atoms called ?

The attraction of cohesion , or simply cohesion.

14. Why do not the atoms rush together, and all bodies become perfectly solid?

Because the heat collected between or around the atoms exerts a repulsion, and keeps them a certain distance apart.

15. How do we know that heat has this effect?

If the heat he increased the particles are forced farther apart, and if it he diminished they draw nearer together.

16. What have you to say of the forces of attraction and repul¬ sion exerted between the atoms of bodies ?

That their energy is enormously great.

17. Illustrate the astonishing energy of the attraction between atoms.

The strongest iron wire, of one quarter of an inch in thickness, could not be broken by the united strength of five horses.

18. Illustrate the repulsion exerted between atoms from the efFect of heat.

The explosive force of gunpowder projects heavy can¬ non balls to great distances, and rends the hardest rocks into fragments.

19. Have substances different mechanical properties?

They have ; for example, iron is hard, and chalk is soft ; glass is brittle , and gold is malleable.

20. Are there any other metals that can be hammered out into leaves, or rolled into sheets, besides gold ?

Silver, lead, aluminum, tin, copper, zinc, platinum, and iron are all malleable.

NATURAL PHILOSOPHY.

21. What is meant when it is said that a certain metal, or other substance, is ductile ?

That it can be drawn out into a wire or thread.

22. What metals are ductile ?

Platinum, silver, iron, copper, and gold. Zinc, tin, and lead are also ductile in an inferior degree.

23. What may be said of melted glass ?

That it is very ductile. It can be drawn out, or spun into fine threads.

24. Why does a piece of India rubber when stretched fly back if left to itself ?

Because the particles, when displaced, tend to recover their original positions.

25. Do we observe the same tendency under other circumstances ?

We do; for example, when we squeeze an India rubber

ball in our hand, or bend a piece of whalebone.

26. What is said of such a substance ?

That it is elastic.

27. Mention other highly elastic substances.

Glass, ivory, steel, air, and all gases.

28. In how many different states does matter exist ?

In three states — solid, liquid , and gaseous. A stone is solid, water is liquid, and air is gaseous.

29. How may a substance be made to pass from one of these states into another ?

By increasing or diminishing the amount of heat which it contains. Water is converted into vapor by heat, and into ice by cold.

MECHANICAL PROPERTIES OF BODIES.

30. Suppose two polished plates of glass or metal are laid one on the other, and slightly pressed ?

It will be found if we undertake to separate them, that they stick together.

31. What is the force that holds the plates together called?

Attraction of adhesion , or simply adhesion.

32. What is the reason that if two panes of common window glass are placed on each other they do not adhere ?

Because they are not even and smooth enough to come into close contact.

33. Mention one or two familiar facts that are to be explained by adhesion.

The marks made in writing with chalk or a lead pen¬ cil ; the sticking of dust to the walls and furniture of rooms.

34. Does adhesion manifest itself between liquids and solicit, as well as between solids ?

It does ; ' if I dip my finger into water it becomes wet, because a film of water adheres to it.

35. Mention other illustrations of adhesion between liquids and solids.

36. Does attraction manifest itself between bodies at a distance, as well as between those which are in close contact ?

It does; the earth attracts all bodies, and causes them, if unsupported, to fall toward its surface.

NATURAL PHILOSOPHY.