other; but that they may be separated under the influence of a power greater than their mutual attraction, and may alter their position around the particles without going out of the sphere of action assigned to them in the neighbourhood of the particles. The fluids are then set with regard to the cardinal points; that is to say, in the magnetic sphere which surrounds each particle, the northern fluid flows constantly in one direction, and the southern fluid in an opposite one; whence arise two resultant forces acting in contrary directions, the points of application of which are the two poles of the magnet. As soon, however, as the setting of the fluid ceases, equilibrium is again established around each particle, and the final result is null, that is to say, there is neither attraction nor repulsion.

put in contact with a magnet, a bar of steel becomes magnetic only by slow degrees. It is even necessary to rub it with one of the poles of the magnet, if we wish to give the whole force of the loadstone. The separation of the two fluids presents a resistance which is not found in malleable iron. It is the same with their recomposition; for a bar of steel, once magnetised, is a very long time before it loses its magnetic power. By oxidation, pressure, or twisting, soft iron may acquire a certain coercive force, but of short duration.

Experiments with Broken Magnets.-The presence of the two fluids in every magnet is demonstrated by the following experiment. Take a steel knitting-needle, which is magnetised by rubbing it over with one of the poles of a magnet. Then having thus proved the existence of the two poles and the neutral The theory of two magnetic fluids readily explains many line by means of the iron filing experiment, break the needle phenomena, and is therefore generally adopted as a means of in the middle, that is to say, at about the neutral line. Now, demonstration. It will be seen, however, hereafter, that in if you bring the two halves successively in contact with the all probability magnetic phenomena result, not from the oppo- poles of a moveable needle fig. 362, you will find that instead of site actions of two particular fluids, but from particular cur- each containing only one fluid, each separate part has its two rents of electric matter in magnetised bodies-an hypothesis poles and its neutral line. If you again break these two magnets which has the advantage of connecting the theories of mag-into two other parts, you will again find that each of these netism and electricity together. again is a complete magnet, with its two poles and neutral Difference between Magnetic Substances and Magnets.-Mag-line, and so on as long as you can break the steel into lengths, netic substances or bodies, are those which are drawn or attracted by the magnet, such as iron, steel, nickel. These bodies all contain the two fluids, but in a neutralised state. Ferruginous compounds are generally magnetic, and are the more so, the more iron they contain. Some, however-as persulphuret of iron for instance-are not attracted by the magnet.

It is easy to distinguish a magnetic substance from a magnet; the former has no poles. On being presented successively to the two extremities of a moveable needle ab, fig. 362, it attracts both, while a magnet would attract one and repel the other, if the same end of the same magnet were presented to them.

Magnetisation by Induction or Contact.-When a magnetic substance is put in contact with a magnetic bar, the two fluids of this substance are separated, and it becomes, as long as the contact lasts, a complete magnet, with its two poles and neutral line. For example, if you apply to one of the poles of the magnet, fig. 364, a small cylinder ab of soft iron, this cylinder Fig. 364.

will in its turn bear a second, then a third, and so on to seven or eight, according to the force of the bar. Each of these little cylinders is a magnet, but only while the influence of the magnetised bar lasts. If the contact between the magnet and the first piece of iron be broken, immediately, or at all events after a very brief interval, the other cylinders are detached and retain no trace of magnetic force. The separation of the two fluids has therefore only been temporary. Nickel is also easily magnetised under the influence of a powerful magnet. Magne isation by contact explains the formation of the tufts of iron filings which cling to the poles of the magnet, fig. 361. The particles in contact with the magnet act upon the next ones, these again upon the following, and so on, which gives rise to the thread-like arrangement of the iron filings around each pole.

Coercive Power-We call that coercive power, which in a magnetic substance more or less opposes the separation of the two fluids, and their subsequent recomposition when they have been separated. From the above experiment, it will be seen that this power is imperceptible in soft iron, this metal being instantly magnetised by contact with a magnet. tempered steel, on the other hand, this power is great, and greater in proportion to the temper of the steel. In fact, when

In

We conclude, therefore, from analogy, that the very smallest parts of a magnet contain both fluids.

Action of Magnets on all Substances Diamagnetism.Coulomb, in 1802, observed that magnets act upon all sub. stances in a greater or less degree; a phenomenon which he demonstrated by causing little bars of various substances to oscillate first between the opposite poles of two strongly magnetised bars, and then away from the influence of any magnet, and comparing the number of oscillations in the two cases in equal times. At first the result of these experiments was ascribed to the presence of ferruginous matters in the substances upon which the experiments were made; but M. Lebaillif, and at a later period Messrs. Becquerel, demonstrated that magnets have really an influence upon all substances. It has been proved that this influence is sometimes attractive, sometimes repulsive. The substances which are attracted are called magnetic bodies, while those which are repelled have been denominated diamagnetic substances. Among these may be mentioned bismuth, lead, sulphur, wax, water, etc. Copper is sometimes magnetic, sometimes diamagnetic, which probably depends on the degree of its purity.

Mr. Faraday, in 1847, noticed that powerful magnets had a strong repelling influence upon flames, which he attributed to a different degree of diamagnetism in gases. M. Edw. Bec querel subsequently made some important experiments on this subject, and found that, of all gases, oxygen has the greatest magnetic power.

Some natural philosophers have described the diamagnetism as a property distinct from magnetism. M. Edw. Becquerel has connected the phenomena of magnetism and diamagnetism by an ingenious hypothesis. He considers that there are not two distinct kinds of action between bodies and magnets; but only one kind of magnetic induction, and that the repul sion exerted upon certain bodies is to be accounted for by the fact that these bodies are surrounded by a medium more magnetic than themselves.

TERRESTRIAL MAGNETISM-THE COMPASS.

The Directing Influence of the Earth on Magnets.--When we hang a magnetic needle by a thread, as in fig. 362, or when we place it on a pivot upon which it can easily turn (fig. 365), we observe that the needle, instead of settling down in any chance position, always ends by becoming stationary in a position which is more or less that of north and south. The same thing occurs if in a vase full of water we place a cork float, and on this lay a little magnetised rod. The cork oscillates at first, and when it stops, the straight line which joins the two poles of the magnet is still about in the direction of the north and south. It must, however, be noted that in this experi ment neither the cork nor the bar moves to the north or south. The action of the terrestrial poles on the magnet is not attrac tive, but merely a guiding influence.

Similar experiments having been made in all parts of the world, the earth has been assimilated to an immense magnet, the poles of which are near the terrestrial poles, and the

neutral line of which coincides very nearly with the equator. It is from this hypothesis that the name of the northern fluid has been given to that which predominates at the northern pole of the earth, and of southern fluid to that which predominates at the opposite pole. According to this supposition, the earth acts on the needles in the same way that a magnet does, the poles of the same name repel, those of the opposite name Fig. 365.

On the other hand, to find the astronomical meridian, when we know the declination, we turn the compass so that the needle may make with the diameter N s an angle equal to the angle of declination and in the same direction. -22° 25' to the West diameter N8 prolonged gives the direction of the astronomical The meridian. This method, however, is only approximative, because of the continual variation of the declination,

In fact, if the right line ce represents the axis of the needle, and the right line ab its magnetic axis (fig. 367), the true declination is not denoted by the arc e N, which is too great, but by the arc a N. Now if we turn the needle, the magnetic

Fig. 367.

axis a b does not take the position a', but comes back exactly to its first direction, while the extremity e passing between the points a and N, describes an arc precisely as much too small as the first arc was too large. The medium between the two arcs observed gives the true declination.

Mariner's Compass.-The directing action of the earth on the magnetised needle has been put to a very important use in the mariner's compass, known also as the variation compass, or sea compass. It is a declination compass used to guide the progress of ships on the sea. Fig. 368 represents it enclosed, in a rectangular box, which is again placed in another large box called the binnacle, fixed to the after-deck of the ship. Fig. 369 is a transverse section. In these two cuts the same letters indicate the same parts of the instrument.

Fig. 368.

The needle ab (fig. 369), which is easily moveable on a pivot, is fixed to the lower surface of a sheet of talc, on which is drawn a star or mariner's card with thirty-two branches, indicating the eight points of the wind, the half and quarter points. In order that the compass may always preserve its horizontal position, in spite of the rolling and pitching of the ship, it is supported by two concentric moveable rings, one round the axis zz, the other round the axis ed, perpendicular to the first, fig. 368.

An opening м, covered with a plate of rough glass, is used to light the compass during the night. For this purpose a lamp placed outside the box, facing the glass pane, throws its light into the inside. The bottom of the cylindrical box o, in which is the needle, is a pane of polished glass, that gives passage to the light to illuminate the sheet of talc t, which bears the mariner's card upon it, and which is transparent. A second pane of glass m covers the compass, and a pivot i, fixed in the centre of the pane, serves to fix a graduated dialplate A, which is only used for taking the bearings of coasts. To guide a ship by means of the compass, the navigator first finds on a naval chart what is the point of the wind the vessel must steer by to reach its destination. Then with his eye fixed on the compass, the helmsman turns the tiller of the rudder until the point fixed on and marked on the card, coincides with an imaginary line passing through the two points c and d, marked on the edge of the box, fig. 368, and which is parallel with the keel of the vessel. The variation, however, of the declination in different parts of the globe, compels navigators continually to correct the observations they make with the compass.

The inventor of the mariner's compass is not known, nor the precise date of its invention. Guyot de Provins, a French poet of the twelfth century, is the first author who speaks of the use of the magnet in navigation. The ancients, who had no knowledge of the compass, enjoyed no better guide thin the sun or the polar star. They were obliged, therefore, to sail in sight of land, or to run the risk of losing their way when the sky was cloudy.

Fig. 369.

LESSONS IN MORAL SCIENCE.-No. III. WHETHER WE ALWAYS DO RIGHT BY OBEYING THE DICTATES OF CONSCIENCE?

THIS is one of the most perlexing questions in the science of morals. Many are of opinion that all that is necessary to render an action good is that the agent act agreeably to the dictates of his own conscience. This may be considered a vulgar opinion, usually taken up without much consideration. But there is an opinion, near akin to this, which has been advocated by some of the greatest men of the age; namely, that men are not responsible for their opinions or belief. It is thought that the adoption of this as a maxim is the only effectual method of putting an end to the bitter animosities and controversies among the advocates of different creeds.

It is not wonderful that they who make moral sense, in

a

sort, infallible, and the ultimate standard of right and wrong, should hold that men cannot go astray if they will honestly listen to the voice of conscience, and obey her dictates?

But as we have shown that conscience is the judgment of the mind respecting duty, and as no man's knowledge is perfect or infallible, it follows, therefore, that so far as there is error in the understanding in relation to matters of duty, just so far the conscience will be misguided. The question st issue, therefore, is whether an action, wrong in itself, can be considered as a good and virtuous action if the agent believes that it is right. If the affirmative were true, then the discovery of truth would be of no value, for obviously upon this principle error is just as good as truth. But as soon would we believe that darkness is as good as light to direct us in the way which we wish travel. Again, this theory supposes that a man is under no law but his own opinion, or the dictates of conscience; that, therefore, which is a sin in one man may be

duty to another in precisely the same external circumstances or erroneous views. Surely, moral depravity cannot be an and relations; which would be to confound all moral distinc-excuse for erroneous opinions. All actions proceed from tions. This theory would go to sanction every form of religion, certain principles; if, therefore, the action is wrong, because however corrupt and superstitious; and to make the vilest of the corrupt principle, the burden of culpability must be immoralities virtuous; for there can be no doubt that the rolled back upon the principle, or state of the soul, which votaries of idolatry, in their most cruel and abominable rites, sends forth evil acts, as a poisoned fountain sends forth delefollow the dictates of an erring conscience. When the heathen terious streams. sacrifice to demons, and when the victim is a human being, or even a first-born son, there is nothing wrong, for all these acts of worship are performed in obedience to conscience. Every species of persecution and the Inquisition itself may be justified on this principle. Instead, therefore, of putting an end to all animosity, it would bring back, in all their horrors, the days of persecution for conscience' sake.

instance? The answer is, that it is as easy to conceive of a faculty by which we can at once perceive the moral character of an act, as of the power of judging of the rectitude of a general rule.

There is a sense in which it may be said, that reason, or the moral faculty having the power of discerning the moral quality of actions, has the rule in itself. If this is all that is intended by a general rule of right and wrong in the mind, there can be no objection to it. This is saying no more than that the mind has a faculty by which it judges intuitively of many moral acts, as soon as they are observed. The idea may be thus illustrated: here is a straight line, as soon as we see it, we perceive it to be straight; there is a crooked line, which at once we perceive to be crooked. There is no need of a rule in the mind, by the application of which we know that the one is straight, and the other crooked. The quality of the lines is seen at once. So of many moral actions, the moment the mind apprehends them, their moral character is perceived.

Here are so many boys going to school. We observe one, who is large and strong, forcibly taking from another, who is small and weak, some fruit which the latter has with much pains gathered for a sick mother. We need no general rule to guide our judgment. We need only to know the real circumstances of the action. That a large and strong boy should by force take away from one weaker than himself, property to which he has no right, and to which the other has a right, is so evidently immoral, that every mind sees the evil at The general law or rule of morals is therefore made up by the observation and classification of particular acts; just as the general law of gravity is formed by observation of particular facts.

once.

All our knowledge relates originally to particular cases; and general ideas and general rules and laws, are formed by a process of the mind, which may be called generalisation or classification,

THE MORAL FEELING WHICH ACCOMPANIES EVERY
MORAL JUDGMENT.

These moral emotions are, however, of very different degrees of intensity in different persons, and in the same persons at different periods of his life. Persons who have been long accustomed to see atrocious crimes committed, lose in time their moral sensibility, and become accustomed to scenes of blood and robbery. In proportion as the minds of men are enlightened by the truth, and their hearts upright, will be the sensibility of the moral faculty. But by committing sin, as well as by observing it, the moral sensibilities are blunted. This want of right feeling in the conscience is what is called a "seared conscience," which expression is borrowed from the effect produced on any part of the living body, by the repeated application of a heated iron. The result is, that, by degrees, the skin thickens, and the sensibility of the seared part is lost, or rendered obtuse.

Besides this feeling of approbation or disapprobation of moral acts, good or evil, there is a peculiar emotion, in relation to moral acts, according to their nature, when performed by ourselves. In this case, the emotion is much more vivid than when we contemplate the same action as performed by another. When a person is conscious of having performed a truly good action, and from the proper motives, he experiences an emotion of pleasure, of a very peculiar and exalted nature. For this emotion we have no distinctive name; it may be called the pleasure of a good or approving conscience. It must not be confounded with self-complacency, or a proud opinion of our own worth, which may also arise from the performance of a meritorious action. The feeling of which mention has been made, is a simple emotion arising in the mind, from the principles of the human constitution, upon the performance of a good action. One reason why it has not been more noticed is, that it has no distinctive name. The emotion experienced on the performance of a wicked action is well known to every one. It has a distinctive appellation-remorse. It is a feeling distinguishable from all others, and more intolerable than any other species of pain. When violent, it often drives the unhappy subject of it to the most desperate acts. It is like a scorpion, stinging the soul in its tenderest part. No language can exaggerate the misery of a soul abandoned to the torture of this feeling. And though in time it may seem to be allayed by forgetfulness of the crime, yet when any circumstance or association brings the evil action distinctly before the conscience, the torment is renewed Thus, acts of iniquity com the time of solitude and reflection; and the sins of youth embitter old age. This feeling often accompanies the sinner to his times of decline, and is the pain which most annoys him on his bed of death. As the feeling accompanies the guilty unto the last moment of their earthly existence, there is much reason to think that it will cause the bitterest anguish

Whether our judgments and feelings are distinct and separate mental exercises, or whether what we call feeling or emotion is only an idea of a more vivid kind, is a question which we need not discuss, as the decision of it is not neces-mitted in heedless gaiety, often produce sensible remorse in sary to our purpose. All men make a distinction between acts which are purely intellectual, and those exercises of mind called emotions; and no practical error can arise from observing this distinction-whether philosophically correct or not. In every case where a moral object or relation comes before the mind, there is a feeling of approbation or disapprobation, according to the moral character of the object, of which we are immediately conscious. This approbation or disapprobation will not be equal in all cases, but exceedingly different in degree. While some moral actions elicit, when perceived, a very slight degree of approbation or disapprobation, others excite strong emotion, the disaporoval arising to indignation, and the approval to admiration.

act.

In every instance where a good act is observed, there is a feeling of esteem for the agent, as well as approbation of the A disposition, too, is felt to bestow some reward on the person who performs a good action. If we see a man, at the imminent risk of his own life, plunge into the sea to save a stranger who has falien overboard, we approve the action, and feel that he deserves a reward. We therefore call it a meritorious action; for the simple idea of merit is that which deserves a reward.

On the other hand, when we are witnesses of a wicked act of an enormous kind, as, for example, a man murdering a good parent or a kind benefactor, without any provocation, but instigated by avarice or resentment-we feel instantaneously a degree of disapprobation which may properly be called indignation. This feeling would be accompanied by a strong desire that condign punishment should be inflicted on the wicked perpetrator of such a deed. It there were no other means of executing justice, we should feel disposed to aid in punishing the culprit; and the idea of snch a person escaping without punishment, is painful to the impartial 1, and revolting to the moral feelings.

of a future state.

BELIEF IN GOD, AS CONNECTED WITH THE OPERA

TION OF CONSCIENCE.

The question is, whether an atheist is completely divested of the feeling of moral obligation. To those who suppose that speculative atheism is impossible, this question will appear irrelevant; for it would be useless to inquire what would be the effect of a state of mind which never can exist.

As, however, the evidences of the actual existence of atheism are as strong as those of most other fundamental errors; and as the doctrine of certain ideas being impressed on the mind in its creation (on which the opinion that men could not become atheists was founded), is now generally exploded, it may be here taken as admitted that there are atheists in the world. The question proposed is therefore a proper subject for consideration. Bishop Warburton in his "Divine Legation of Moses," seems to adopt the opinion, that a belief in the being of God is requisite to the exercise of conscience, or the sense of moral obligation. But his reasonings on the subject are by no means satisfactory. If we may refer to the experience of the atheist himself, he will assure us, that he perceives the difference between right and wrong, as plainly as others, and that he is conscious of being under a moral obligation to pursue a virtuous course. This, however, they consider an instinctive or constitutional principle, which should be obeyed, just as our appetites and other natural propensities should be obeyed,