E are all children of one Father, and His works it should be our delight to study. As the child, standing by its parent's knee, asks explanations alike of the simplest phenomena and of the most profound problems, so should man, turning to Nature, the living, visible oracle of his Creator, continually ask for knowledge.

In scientific language, Nature is defined as "the united totality of all that the senses can perceive;" in the language of theology, it "embraces everything that cannot be made by man," hence is synonymous with "God's creation."

In Nature there is no such thing as chance. Every effect has its cause, as Nature herself is but a name for an effect whose cause is God. When Newton observed an apple fall to the ground he asked the cause, and in answer to his inquiry came one of the grandest discoveries of science-a discovery which let in a flood of light upon the human mind, and led the way to the true knowledge of many things theretofore shrouded in error or mystery. Montgolfier first conceived the idea of air-balloons while watching fogs floating in the atmosphere, and all the

wonderful discoveries of science may thus be traced to simple phenomena, carefully pondered and diligently studied in all their bearings as to cause and effect.

"Nature," says Whipple, "does not capriciously scatter her secrets as golden gifts to lazy pets and luxurious darlings, but imposes tasks when she presents opportunities, and uplifts him whom she would inform. The apple that she drops at the feet of Newton is but a coy invitation to follow her to the stars." The greatest philosophers have been those who have clung to the demonstrative sciences, and have held that a simple truth, well ascertained, is greater than the most ingenious theory founded upon questionable premises. The discoveries of Newton have borne the searching test of time because he snatched at nothing, leaped over no chasm to establish a favorite dogma, but learned to read Nature correctly by regarding the merest trifles as well as the highest phenomena. Thus he discovered a letter in each atom, a word in each blade of grass, a sentence in each phenomenon, and in the volume thus composed he read the wisdom and the power of the Almighty. Every flower, every ray of light, every drop of

dew, each flake of snow, the lowering cloud, the bright sun, the pale moon, the azure of the heavens by day and the twinkling stars of night, all are eloquent of the great Hand that made them.

From the earliest ages man has sought to read the open leaves of the book of Nature, but even now, after centuries of research and discovery, he does not grasp it all, cause and effect being followed up step by step until the mind is lost in the search. One discovery only leads to another, and the scientist of twenty centuries hence will be compelled to acknowledge that one-half of the wonderful book is still a mystery. However, all may peruse its pages, and all will find pleasure and profit in observing what is daily going on around them in earth, sea and sky. It is, indeed, only by a study of the material world that discoveries are accomplished. Let an attentive observer watch a ray of light passing from the air into the water, and he will see it deviate from the straight line by refraction. Let him seek the origin of a sound, and he will discover that it results from a shock or a vibration. This is physical science in its infancy.

In the pages following it is purposed to present in brief and entertaining form much useful as well as practical scientific knowledge. It has been sought to convey to the mind of the uninitiated, in as simple and practical a way as possible, a general idea of the various branches of science, as well as to state scientific facts briefly and in proper consecutive order, in such a manner that the advanced student may freshen his memory and revive his interest. Technical terms have been avoided as much as possible, and where they are used of necessity the context will furnish ample explanation.

When a person who is a stranger seeks to be

With

directed to some point in a large and poorly laid-out city, whose streets, courts and places start from everywhere and end nowhere, crossing each other in a perverse and confusing manner, it were worse than useless to attempt to give him all the directions at once. The better way would be to point out to him the general direction, and then let him inquire as he progresses on the journey. In this connection it may be said that there is nothing so conducive to loss of time as short cuts to those who are not familiar with them. They generally verify the axiom that "Haste makes waste." these introductory remarks we will take the reader to the broad fields of Science, and point out to him the general direction of the respective paths, noting in our way the most prominent turns, and if our readers desire more specific information we will refer them to the writings of those great men who have devoted their lives to the solution of Nature's problems, and have enabled us to give the reason for many things which, but for their genius and unremitting labors, would still be shrouded by the veil of ignorance.

Among the various works that have aided in the familiar exposition of science presented in this work may be mentioned the following: "Les Récréations Scientifiques," by Gaston Tissandier; "Astronomy," in the series of New Works on Physics by J. A. Gillet and W. J. Rolfe; "Physik und Meteorologie," by Dr. E. Lommel; "The Teacher's Examiner," by A. H. Thompson; "Guide to Familiar Science," by Rev. E. C. Brewer; "Lockyer's Solar Physics," Newcomb's "Popular Astronomy," etc., etc. We desire in an especial manner to thank Professors Rolfe and Gillet for the use of a number of beautiful and accurate astronomical illustrations from their excellent work.

ATURE is revealed to us by objects and by phenomena. An object is a thing which occupies space and which is susceptible to feeling and to sight. The heavenly bodies may also be classed as objects, although we cannot touch them. Phenomena include those results which are perceptible by only one sense, as thunder. Light and sound may also be classed as phenomena. A stone is a natural object. We take it up, open our fingers, and it falls. The motion of that object is a phenomenon. We know it falls because we see it fall, and it possesses what we term weight; but we cannot tell why it possesses weight. A cause of a phenomenon being independent of human will is called a force, and the stone falls by the force of gravitation, or that natural law which compels every material object to approach every other material object. A single force may produce a great number of phenomena.

Nature being revealed to us by objects, and by means of phenomena, we have two branches of science extending from such roots, namely, NATURAL HISTORY, the Science of Objects; and NATURAL PHILOSOPHY, the Science of Phenomena. Both of these branches have been subdivided thus: Zoology, referring to Animals. Botany, referring to Plants. Mineralogy, referring to Minerals, etc. Geology,

Natural History.

Natural Philosophy.

} Biology.

Physics. Phenomena without essential change of the objects.

Chemistry. Phenomena with change of the objects.

Physiology. Phenomena of animated objects.

The two great divisions comprehend, in their extended senses, all that is known respecting the material world.

We have spoken of objects. Objects occupy space. What is space? Space is magnitude which can be conceived as extending in three directions-length, breadth and depth. MATTER occupies portions of space, which is infinite. Matter, when

finite, is termed a body or object. A molecule is the smallest portion of a body which we can conceive of as retaining its identity. An atom is a division of a molecule.

Suppose we take a quantity of water and conceive it to be divided until we reach a limit. The last particle which we could call water would be a molecule. Now let a current of electricity be passed through a quantity of water, and it is separated into two gases, essentially different from each other, and different from water. A given quantity of water will produce a certain quantity of gas, the proportion in volume of the two kinds being as I to 2. If one pint, say, of water produces one volume of one gas, and two of the other, one-half pint would produce one-half the amount of one gas and one-half the amount of the other, and so on down until we have made the ultimate division, which, for convenience, we call a molecule. Then we can truly say that the molecule is composed of two parts of one gas and one part of the other, and for convenience we call these parts of the molecules, atoms.

Physics deals only with masses and molecules. Chemistry deals with atoms. When we tear a piece of paper in pieces, or grind it to a pulp, we separate molecules and have effected a physical change only. When we burn the paper in the fire we separate atoms and have effected a chemical change. In the first case we have effected a change of form, but the matter is identically the same. In the second case, the gases and ashes produced by the burning are totally different, and the paper has lost its identity.

The sounding of a bell and the falling of a stone are physical phenomena, for the object which causes the sound or the fall undergoes no change. Heat is set free when coal burns, and this disengagement of heat is a physical phenomenon; but the change during combustion which coal undergoes is a chemical phenomenon.

The General Properties of Matter

Are magnitude, impenetrability, inertia, divisibility, porosity, elasticity, compressibility, expansibility and indestructibility. Magnitude is the property of occupying space. Size is the amount of space a body fills. Every body has three dimensions -length, breadth and thickness; and, in order to measure these, some standard of measurement is required.

Impenetrability is the property of so occupying space as to exclude all other bodies; for no two bodies can occupy the same space at the same time. We sometimes speak of one substance penetrating another. Thus, a needle penetrates cloth, a nail penetrates wood, etc.; but on a moment's reflection it will be plainly seen that they merely push aside the fibers of the cloth or wood, and so press them closer together. Inertia is the property of passiveness. Matter has no power of putting itself in motion when at rest. A body will never change its place unless moved, and if once started will move forever unless stopped. It is difficult to start a wagon because we have to overcome its inertia, which tends to keep it at rest. When the wagon is in motion it requires as great an exertion to stop it, since then we have again to overcome its inertia, which tends to keep it moving.

Inertia causes the danger of jumping from cars when in motion. The body has the speed of the train, while the motion of the feet is stopped by contact with the ground. One should jump as nearly as he can in the direction in which the train is moving, and with his muscles strained, so as to break into a run the instant his feet touch the ground. Then with all his strength he can gradually overcome the inertia of his body, and after a few feet can turn as he pleases.

Divisibility is that property of a body which allows it to be separated into parts. It would be impossible to find a particle so small that it still could not be made smaller. Practically speaking, there is no limit to the divisibility of matter; but philosophers hold that there is in theory. When we attempt to show how far matter can be divided, the brain refuses to grasp the infinity. A pin's head is a small object, but it is gigantic compared to some animals, of which millions would occupy a space no larger than the head of a pin. These tiny animals must have organs and veins, and those veins must be full of blood globules. Prof. Tyndall says a drop of blood contains three millions of red globules. But there is something even more astonishing than this. It is stated that there are more animals in the milt of a single codfish than there are men in the world; and that one grain of sand is larger than four millions of these animals, each of which must be possessed of life germs of an equal amount, which would grow up as it grew to maturity. This carries us back again, and

"Imagination's utmost stretch In wonder dies away."

Porosity is the property of having pores. By this is meant not only such pores as are familiar to all, and to which we refer when, in common language, we speak of a porous body, as bread, wood, unglazed pottery, a sponge, etc., but a finer kind, as invisible to the eye as the atoms themselves. These pores are

caused by the fact that the molecules of which a body is composed are not in actual contact, but are separated by extremely minute spaces.

Elasticity is classed both among the general and the specific properties of matter. It is thought that all bodies have elasticity, yet some have it in such a degree that it serves to distinguish them from other bodies.

Compressibility is that property of matter by virtue of which it may be made to occupy less space. It is a result of porosity, the molecules being pressed closer together.

Expansibility is the opposite of compressibility. Indestructibility is the property which renders matter incapable of being destroyed. No particle of matter can be annihilated, except by God, its creator. We may change its form, but we cannot deprive it of existence.

The Specific Properties of Matter

Are those which are found only in particular kinds of matter. The most important are ductility, malleability, tenacity, elasticity, hardness and brittleness.

A ductile body is one which can be drawn into wire. Some of the most ductile are gold, silver, and platinum.

A malleable body is one which can be hammered or rolled into sheets. Gold is the most malleable of all metals, and can be beaten into sheets of an inch in thickness. Copper is

so malleable that it is said that a workman, with his hammer, can beat out a kettle from a solid block of the metal.

A tenacious body is one which cannot be easily pulled apart. Iron is the most tenacious of the metals.

There are three kinds of elasticity-elasticity of compression, elasticity of expansion, and elasticity of torsion.

Solids-Liquids-Gases.

Matter is present in Nature in three conditions. We find it as a solid, a liquid, and a gas. To test the actual existence of matter in one or other of these forms our senses help us. We can touch a solid, or taste it and see it. But touch is the test.

A solid is a body whose molecules cohere so that their rela tive positions cannot be changed without the application of considerable force. A solid will retain any shape given it.

A liquid is a body whose molecules cohere so slightly that their relative positions may be changed on the application of slight force. A liquid will assume the form of the vessel containing it, and the free surface will always be horizontal, each molecule seeking its lowest level by the force of gravity. A gas is a body whose molecules separate almost indefinitely from each other. Essentially there is no difference between a gas and a vapor. The term gas is generally applied to those bodies which are ordinarily in a gaseous state, and the term vapor to that which is formed by heating a liquid or solid. Steam is the vapor of water, but it is a gas as much as oxygen or hydrogen.

The Forces of Nature.

Force is a cause-the cause of motion or of rest. It requires force to set an object in motion, and this object would never stop unless some other force or forces prevented its movement