mal substances are formed chiefly of these three elements, with the addition of nitrogen. So largely does oxygen enter into combinations with other elementary substances, that one half of the entire globe itself is said to be formed of this gas, or, as one writer has expressed it, "of compressed and hardened air."

4. How one substance can assume forms and properties so different as charcoal and the diamond, or how two or more substances, merely by different combinations of them, can produce things so totally unlike as common air and nitric acid, or as sugar and vinegar, we are unable to conceive; but chemistry teaches us the facts, and leaves us to ponder over such mysteries in wonder and admiration. But it is not merely a science that is full of wonders; in its various departments it is intimately related to all the other natural sciences, and it forms the basis of all the useful arts. Thus, what is termed Inorganic Chemistry treats of the laws of combination by which are formed all those compound bodies which are not the products of organized life. There is not a single manufacture or art, from the smelting of ore and the making of bread, to the manufacture of gunpowder and electric telegraphing, that is not more or less dependent upon · this branch of chemistry.

5. In what is called Organic Chemistry we trace the combinations of the same elementary substances, and chiefly the three gases and carbon, as modified by the principle of life; and thus animal and vegetable chemistry are recognized as branches of one greater science. In Agricultural Chemistry we study the applications of chemistry to agriculture; and being made acquainted with the chemical ingredients of plants and soils, we are enabled so to avail ourselves of the laws of vegetable growth as to adapt our soils to the nature of the product required. Indeed, so extensive are the applications of chemical principles, that they enter, in some mode or form, into every branch of industry, and every department of civilized life.

LESSON II.-FIRST PRINCIPLES: ULTIMATE ATOMS.

1. WHEN a stick of wood is burned for fuel, it is destroyed as a stick of wood, but not one of the particles, or, more properly, atoms, which composed it, has been annihilated. In the ashes of the wood, and in the atmosphere in which it was

Some of these atoms

consumed, every atom must still exist. may glisten in the morning dew, crystallize in the snow-flake, or fall to the waiting fields in the grateful rain. Other atoms of the stick of wood apparently destroyed may appear the next year in some stick of sugar-candy, and again, ages hence, may constitute a little but important part of some votive monument of marble. Such changes are not only possible, but probable.

2.

3.

4

5.

When by the wind the tree is shaken,
There's not a bough or leaf can fall,
But of its falling heed is taken

By One that sees and governs all.
The tree may fall and be forgotten,
And buried in the earth remain;
Yet from its juices rank and rotten
Springs vegetating life again.
The world is with creation teeming,
And nothing ever wholly dies;

And things that are destroyed in seeming,
In other shapes and forms arise.

And Nature still unfolds the tissue

Of unseen works by spirit wrought;
And not a work but hath its issue

With blessing or with evil fraught.-KENNEDY,

6. The journey of an atom in its ceaseless round would be even more wonderful than the adventures of a drop of water -now in the ocean, next in the rainbow, then a part of an iceberg, and again on its way to the purple cloud. The ocean has been in the clouds-perhaps many times; and yet, in all its changes, not a particle has been lost.

7.

"Nothing is lost: the drop of dew

Which trembles on the leaf or flower,

Is but exhaled to fall anew

In summer's thunder-shower;
Perchance to shine within the bow

That fronts the sun at fall of day,
Perchance to sparkle in the flow
Of fountains far away."

8. The plant is made of the mineral, and the animal consumes the plant and returns to the earth, again to enter into new combinations. Shakspeare says,

"Imperious Cæsar, dead, and turn'd to clay,
Might stop a hole, to keep the wind away;
Oh that the earth, which kept the world in awe,
Should patch a wall to expel the winter's flaw !"

9. Another has expressed the same truth in the following words: "Man, moving to-day the monarch of a mighty people, in a few years passes back to his primitive clod, and that combination of elementary atoms which is dignified with the circle of sovereignty and the robe of purple, after a period may be sought for in the herbage of the fields and in the humble flowers of the valley."-HUNT.

10. We live in a world of change. The growth and composition of organic matter, the rusting of metals, the crumbling of rocks, and the combustion of fuel, afford innumerable illustrations of this truth. Nothing is at rest-nothing is permanent; and yet, in all the changes which matter has undergone, from creation's dawn to the present time, we have no reason for believing that the minutest atom has been destroyed. Let not man, then, contemn the atom which he could not create, and which he has not the power to destroy.

LESSON III.-THE MAN AND THE ATOM.

1. "SMALL atom, unconsidered,

Unfelt, and scarcely seen!

Thou hast no worth upon the earth

So infinitely mean.

2. "Useless thou art, oh atom'!
And, absolute in might',

If I decree thou shalt not be',
I can destroy thee quite."

3. "Ah! no; thy hand is powerless.
I hold a life too high;

A strength innate, as old as fate;
I change, but can not die.

4. "Destruction can not touch me;
The hand alone which wrought
My shape and thine-a hand divine-
Can hurl me into naught.

5. "Thou mayst on waters cast me,
Or loose me to the wind,
Or burn in fire, at thy desire,
So that thou canst not find;

6. "But I shall hold existence
To earth's remotest time,
And fill in space my destined place,
Though humble, yet sublime.

7. "Ere yet offending Adam

Fell from his pure estate,

Or tended flowers in Eden's bowers,
With Eve, his happy mate';

8. "I, even I, existed,

And played my proper part
In God's great plan-oh, little man,
Reflect on what thou art!

9. "Couldst thou destroy my being',
Thy hand might reach the spheres',
And bid the sun no longer run
His course among his peers.

10. "Be humble', brother atom';
Whate'er thy mortal growth

Or mine may be, humility

Alone becomes us both."-C. MACKAY.

LES. IV.-CHEMICAL AGENTS: HEAT-LIGHT-ELECTRICITY.

1. THE number of substances not known to be compounds is upward of sixty; the names of which, the symbols by which they are designated in chemical books, and their combining proportions, are given in a note at the bottom of page 426. Nearly half of these elements, as they are called, are of rare occurrence, and not more than twenty of them are of much interest to any but the professed chemist. It is with these elements, which make up the whole material world, that chemistry deals; and its province is to point out and explain the agencies or active forces employed in effecting changes among them, the laws under which these changes are made, the properties of the elements and of their compounds, and, finally, the applications of the science to arts, manufactures, and agriculture. The latter division of the subject, although of exceeding interest and importance, must be reserved for the Sixth Reader.

2. The active forces of chemistry are heat, light, and electricity. By their separate or combined action the elements of matter are caused to unite, and sometimes compounds are decomposed into their original constituents, and new substances are formed.

3. Let us first glance at some of the chemical effects of heat. The matters of every-day life will furnish us abundant examples. Lead is one of the elementary substances. And who has not observed that when lead is melted, a scum or dross covers the surface, and that if it be kept long in a melted state it will disappear as metallic lead, and become dross altogether? But what has become of the lead? The heat has caused it to unite with a portion of the oxygen from the air, and form this dross; and if the heating process be continued long enough, the dross will unite with more oxygen and become red-lead, a substance used in painting. The manufacture of this important article of commerce is merely an application of the chemical principle here illustrated-the combination of oxygen with common lead.

4. The red rust on iron nails and bolts found among the ruins of burned buildings shows that heat facilitates the com

bination of iron and ogygen. It is frequently the case that one degree of heat will cause oxygen to unite with a metal, while a higher degree will cause a separation. It is the tendency of heat, moreover, to separate, in a greater or less degree, the particles or atoms of which a body is composed, and thus to enlarge its bulk so long as the force of heat is exerted. Advantage is taken of this expansive property in liquids in the construction of thermometers.

5. Light is another important chemical agent often associated with heat. But they may be separated from each other; and it can be proved that there is no correspondence between intense light and ardent heat. Milton says, addressing Light:

"Before the sun,

Before the heavens thou wert, and at the voice
Of God, as with a mantle, didst invest

The rising world of waters dark and deep,

Won from the void and formless infinite.'

6. As the cause of color, as the medium of vision, and as an agency influencing in a most striking manner all the forms. of organization, and even affecting the crystallization of inorganic matter, light has always presented to inquiring minds a subject of the highest interest. Light paints the blush on the luscious peach, and spreads the "tender green" over the leaves of the forest and the grass of the meadows. The very shells of the ocean are almost colorless when taken from great depths, where the action of light is but feeble.

.

7. We see, daily, numberless instances of the chemical ef fects of light. In the sunshine some colors fade, and others become more intense. Many vegetables can be kept better in places deprived of light, and certain medicines must be kept in black bottles, or be otherwise protected from solar influence. Daguerreotypes and photographs are made by the chemical action of light on certain preparations of silver, or other substances very sensitive to its influences.

8. A mixture of two gaseous elements, chlorine and hydrogen, may be made in the dark, without exhibiting any tendency to unite; but if the bottle containing them be exposed to the sunlight, a violent explosion ensues, and a compound is formed, which is called hydrochloric acid.

9. Not only is light an indispensable agent in the growth of vegetables, but it is necessary to the proper development of animal life. How sensitive are our bodies to its influences! How our feelings sympathize with every change of the sky! When the sun shines, the blood flows freely, and our spirits are light and buoyant. Professor Johnston has said, in his