cut perpendicularly to the axis and fixed in a cork. Then | the glass n, fig. 349, being inclined in such a manner as to transmit a polarised pencil to the quartz, look through a double refracting prism g, fig. 350, at the same time turning the tube in which this prism is, and you will observe the complementary images produced by the passage of the polarised light through the quartz.

Rotatory Power of Liquids.-Quartz is the only solid in which circular polarisation has been observed, but Biot found the same property in many liquids and solutions. The same philosopher observed that the displacement of the plane of polarisation may exhibit differences in the composition of bodies, which could not be detected by any chemical analysis. For example, sugar obtained from the grape turns the plane of polarisation to the left, while sugar from the cane turns it to the right, though the chemical composition of the two substances is the same. Biot found that the rotatory power of liquids is much less than that of quartz. For instance, in concentrated syrup of sugar from the cane, which is one of the liquids possessing the rotatory power in the highest degree, this power is thirty-six times less than in quartz, in consequence of which it is necessary to experiment upon liquid columns of considerable length, that is to say, about eight inches.

ether, which shows that the plane of polarisation has not turned. But if we fill the tube with a solution of cane sugar, or any other active liquid, the extraordinary image reappears, and to destroy it we must turn the disc a certain number of degrees to the right or left of zero, according as the liquid is dextrogyral or lævogyral, which proves that the plane of polarisation has turned through the same number of degrees. With solution of cane sugar, the rotation takes place to the right, and if with the same solution we take tubes of greater length, we find the rotation is increased in proportion to the length, according to Biot's second law. Lastly, if with a tube of constant length we take solutions containing more and more sugar, we find the rotation increase in proportion to the increase of sugar, whence we see that from the angle of deviation we may deduce the quantitative analysis of the solution.

Soleil's Saccharimeter.-Soleil availed himself of the rotatory property of liquids, which was discovered by Biot, to construct an apparatus for analysing sacchariferous (or sugar-bearing) substances, to which is given the name of saccharimeter. Fig. 352 represents the saccharimeter placed horizontally, and fig. 353 represents a longitudinal section, with all the recent modifications introduced by Doboscq, Soleil's son-in-law and successor. This instrument, which is apparently simple, is very complicated in a theoretical point of view, for it presupposes a knowledge of the principal phenomena of double refraction and polarisation. The principle of this apparatus is not the amount of the rotation of the plane of polarisation, Fig. 352.

Fig. 351 represents the apparatus employed by Biot to measure the rotatory power of liquids. In a copper channel 9, fastened to a support r, is a tube about eight inches long, containing the liquid on which we wish to experiment. This tube

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is plated internally and terminated at the ends by two parallel | like that of Biot, above described, but compensation, that is to glasses, fastened by two collars with screws. At m is a black say, the employment of a second active substance, acting in a glass, making with the axis of the tubes b, d, and a, which is direction opposite to that in which we wish to analyse, and the same for all three, an angle equal to the angle of polarisa- the thickness of which may be varied until the contrary tion, the consequence of which is, that the light reflected by actions of the two substances destroy each other; so that, the glass m in the direction b da, is polarised. In the centre instead of measuring the deviation of the plane of polarisation, of the divided circle h, in the tube a, and perpendicular to the we measure the thickness to be given to the compensating axis b da, is a double refracting achromatic prism, which can substance (which is a plate of quartz), to obtain a complete be turned at will round the axis of the apparatus by means compensation. There are three principal parts in the appaof a button n, fastened to a dial plate with a vernier, which ratus; a tube containing the liquid to be analysed, a polariser, indicates the number of degrees through which the prism is and an analyser. The tube m, which contains the liquid, is turned. Lastly, the plane of polarisation so d, of the reflected of copper, plated inside, and terminated at its two extremities penc.l is vertical, and the zero of the graduation on the circle by two glasses parallel to each other. It rests upon a support h, is in this plane. Before the tube d, is placed in the channel, which has at its ends two tubes, a andr, in which are the 9, the extraordinary image given by the double refracting crystals that serve as polarisers and analysers, and are repreprism vanishes, as often as the disc e, corresponds to the zero sented in fig. 353. of the graduation, because then the double refracting prism is turned in such a manner, that its principal section coincides with the plane of polarisation. It is the same when the tube d is full of water or any other inactive liquid, like alcohol or

Before the orifice e (fig. 353) is placed a moderator lamp, the light proceeding from which, in the direction of the axis of the instrument, meets a double refracting prism r, which acts as a polariser. Only the ordinary image reaches the eye,

allow none but red light to pass. An opaque screen e, with a thin edge, placed behind the lens and beyond its focus, intercepts half of the luminous cone, while the other half is projected upon a screen 6, the front view of which is at B. We then observe, within the geometrical shadow bounded by the straight line ab, a reddish and rather bright light, which decreases in brightness in proportion as the points of the screen are more distant from the boundary line of the shadow, and on the part of the screen which ought to be uniformly lighted are seen fringes alternately bright and dark, which grow gradually feebler till they completely disappear.

All the various colours of the spectrum give rise to the same phenomenon, but with this distinction, that the fringes are narrower, and consequently less dilated, in proportion as the light is less refrangible. The result of this last property Fig. 333.

Fig. 358.

things-a judgment and an emotion, or feeling of a peculiar for perceiving peculiar qualities in certain appropriate objects. kind.

2. Alli udgments of the mind, whatever be the subjects of em, appertain to the understanding. This comprehensive faculty includes all intellectual acts, whether relating to external objects, mathematical relations, natural beauty and sublimity, or moral duty. So far, therefore, as conscience is a judgment respecting any moral subject, so far it is an exercise of the understanding. We have not one faculty by which we discern physical truths, another by which we judge of mathematical theorems, and another for matters of taste; but all these are the one and the same understanding, exercised on different objects. Accordingly, when moral qualities are the objects of our contemplation, it is not a different faculty from the reason or understanding which thinks and judges, but the same, exercised on other subjects; and the only difference is in the object. Our conclusion therefore is, that so far as conscience is an intellectual act or judgment of the mind, so far it belongs to the understanding.

3. But as more is included under the name conscience than a mere intellectual act or judgment, and as this judgment is attended with a peculiar feeling, called moral, and easily distinguished from all other emotions; and as mere emotion or feeling can with no propriety be referred to the reason, therefore conscience is, so far as this is concerned, different from the understanding.

4. If the moral judgments of the mind proceeded from a faculty distinct from the understanding, and often differing from it, the harmony of the mental operations would be destroyed. While reason led to one conclusion, conscience might dictate the contrary. And upon this theory, conscience must always be correct, unless the faculty be morbid.

All experience and history show that men may act under the influence of an erroneous conscience. The dictates of conscience are always in conformity with the practical judgments of reason. When these are erroneous, conscience is erroneous. The conclusion therefore is, that conscience is not a distinct faculty from reason, so far as it consists in a judgment of the quality of moral acts. Reason or understanding is the genus; the judgments of conscience are the species. Reason has relation to all intelligible subjects; the moral faculty is conversant about moral qualities alone.

THE MORAL SENSE COMPARED WITH THE TASTE. From what was said in the preceding remarks it appears that conscience, or the moral sense, is not a simple but a compound faculty, including both an intellectual act or judgment, and a peculiar feeling or emotion. The name moral sense was probably adopted to express this feeling, or internal emotion. It will serve perhaps to illustrate this subject, if we bring into view another faculty, between which and the moral sense there is a remarkable analogy. I refer to what is commonly called Taste, or that faculty by which men are in some degree capable of perceiving and relishing the beauties of nature and art. In this there is a judgment respecting that quality denominated Beauty, but there is also a vivid emotion of a peculiar kind accompanying this judgment. The external objects in which beauty is resident might be distinctly seen, and yet no such quality be perceived; as was before mentioned in regard to certain animals, whose sight and hearing are more acute than those of men, and which yet appear to be utterly insensible of the quality called beauty.

If the question should be raised whether Taste is merely an exercise of the understanding, the proper answer would be precisely as in the case of conscience, viz., so far as it consists in judgment, it appertains to the intellectual faculty; but so far as it consists in emotion, it does not. And in this as in matters of conscience, errors of judgment will affect the emotions produced. In cultivating Taste, it is of the utmost importance that correct opinions be adopted in relation to the objects of this faculty.

The question may perhaps be asked, why either of these should be considered a distinct faculty of the mind. In regard to mental faculties or powers, there is a want of agreement among philosophers, as to what is requisite to entitle any mental operation to be referred to a distinct and original faculty. In these two cases, there exists in the mind a capacity

Though the ideas of beauty and morality are judgments of the understanding, it requires a faculty suited to the objects to enable the understanding to obtain the simple ideas of beauty and morality. We can conceive of a rational mind without such a capacity. There is also in these faculties, the suscepti bility of a peculiar emotion, dissimilar from all others; and these two things constitute the faculty of Taste or Conscience. But it is a matter of no importance whether taste and conscience be called distinct and original faculties, if what has been said respecting their nature be admitted.

There is in the human mind a capacity of discerning what is termed beauty, in the works of nature and art. This judgment is accompanied by a pleasurable emotion, and to this capacity or susceptibility we give the name Taste. There is also a power of discerning moral qualities, which perception is also attended with a vivid emotion; and to this power or faculty we give the name Conscience, or the moral faculty. Both these are so far original parts of our constitution, that if there did not exist in every mind a sense of beauty and its contrary, and a sense of right and wrong, such ideas could not be generated or communicated by any process of education.

MORAL OBLIGATION.

Much has been written to explain the true ground of moral obligation. But the subject has been rather darkened and perplexed than elucidated by these comments. It is always so when men undertake to explain that which is so clear that it needs no explanation.

Every idea of morality includes in it that of moral obligation. A moral act is one which ought to be performed; an immoral act is one which ought not to be performed. As soon as we get the conception of a moral act, we receive with it the idea of moral obligation. It would be a contradiction to say that any act was moral, and yet that there was no obligation to perform it. One of the best definitions which can be given of a moral act is, that it is an act which we are bound to perform, and of an immoral act, that it is one which ought not to be done. The more clearly we see anything to be moral, the more sensibly we feel ourselves under a moral obligation to perform it. This being a matter of common intuition and universal experience, all that is necessary to convince us of its truth, is to bring it distinctly before our minds. There is therefore no need to look any further for the grounds and reasons of moral obligation, than to the morality of the act itself, as this idea is involved in every conception of morality.

The following citation from Dr. Price's work on Morals is in accordance with the view just given: "From the account given of obligation, it appears how absurd it is to inquire, what obliges us to practise virtue? as if obligation were no part of the idea of virtue, but something adventitious and foreign to it: that is, as if what was our duty might not be our duty; as if it might not be true, that what is fit to do, we ought to do, and that what we ought to do, we are obliged to do. To ask why we are obliged to practise virtue, to abstain from what is wicked, or perform what is just, is the very same as to ask why we are obliged to do what we are obliged to do. It is not possible to avoid wondering at those who have so unaccountably embarrassed themselves on a subject that one would think was attended with so little difficulty: and who, because they cannot find any thing in virtue and duty themselves, which can induce and oblige us to pay a regard to them-fly to self-love, and maintain that from hence alone are derived all inducement and obligation." Dr. Paley commences his second book on Moral Philosophy by an inquiry into the nature of moral obligation. He asks, "Why am I obliged to keep my word?" and mentions several answers which would be given by different persons, and which he says all coincide. But he goes on to say that all the answers leave the matter short; for the inquirer may turn round upon his teacher with a second question, "Why am I obliged to do what is right, to act agreeably to the fitness of things, to conform to reason, nature or truth, to promote the public good, or to do the will of God?"

All this, it appears to us, is fitted to mystify as plain & subject as ever engaged the thoughts of a rational mind, and is designed to remove the true ground of moral obligation, and

which is in itself right. The conflict is not between a greater and a less happiness, but between the prospect of happiness and moral obligation.

reduce all such obligation to the single principle of self-love, or the tendency of an act to promote individual happiness. Suppose that, after Dr. Paley had made all obligation to rest on the ground that the performance of a good act promotes On this subject, the appeal must be to the common judgour eternal happiness, the inquirer should again ask, "Why ment of men. And we are persuaded that this confounding of am I bound to perform that which will promote my happiness?" moral obligation with motives of another kind, is a radical The question, indeed, would be unreasonable, because all men defect in Dr. Paley's system, which-lying at the foundation are agreed that happiness is a good; but is it not equally-vitiates the whole, and has already been the cause of great unreasonable, when an action is seen to be virtuous, or morally evil to society. right, to ask "Why am I obliged to do it?" The moment we see a thing to be morally right, the sense of obligation is complete, and all further inquiring for reasons why am I obliged to do right is as absurd as would be inquiring for reasons why I should pursue happiness.

Where we have intuitive certainty of any thing it is foolish to seek for other reasons. If there is anything clear in the view of a rational mind, it is this: that virtue should be practised, that what is right should be done. But still further to perplex this plain subject, Dr. Paley has undertaken to inform us what is meant by obligation. "A man," says he, "is said to be obliged when he is urged by a violent motive resulting from the will of another."

This is, indeed, a very extraordinary definition. The motive he says must be violent; but why may not a motive which is not violent create an obligation according to its force? The main error of this definition is, that it confounds moral obligation with other motives of an entirely different kind. The obligation of which he speaks is created by the will or command of another. The law of a tyrant requiring his subjects to do what is evidently wrong cannot create a moral obligation. A rational being may be urged by the threats of a tyrant, on the universal principle of self-love, and this force may, by an abuse of terms, be called an obligation; but according to the common usage of the language, when a man is said to be under obligation to perform an act, we mean that he is morally bound. But whether the operation of any violent motive, resulting from the will of another, may be said to oblige a man or not, the main inquiry is, what is the ground of moral obligation? The difference between a moral obligation and other motives which may oblige should be kept in view. He then returns to the question, "Why am I obliged to keep iny word?" and applies the preceding definition of the nature of obligation, and gives the following answer: "Because I am urged to do so by a violent motive (namely, the expectation of being after this life rewarded if I do, or punished if I do not), resulting from the command of another (namely, of God)." He goes on to say, "When I first turned my attention to moral speculations, an air of mystery seemed to hang over the whole subject, which arose, I believe, from hence; that I supposed with many authors whom I had consulted that to be obliged to do a thing, was different from being induced to do it; and that the obligation to practise virtue, and to do what is justice, is quite another thing and of another kind from the obligation which a soldier is under to obey his officer, or a Servant his master, or any of the ordinary obligations of

human life."

We cannot but be of the opinion that Dr. Paley has here made a radical mistake, which it is exceedingly important to consider, since, unhappily for sound morals, his system is so much employed in the instruction of youth.

The theory of morals, of which the above principle is a part, is no other than this: that the only difference between virtue and vice consists in their tendency, respectively, to promote or hinder the happiness of the individual; so that if a man could persuade himself that no evil would arise to him from telling a lie, he would be under no obligation to speak the truth. It is a scheme of morals which obliterates all intrinsic difference between virtue and vice, and makes the one preferable to the other on no other account than its tendency to promote individual happiness in the future world.

If a man does not believe in a future world, he can, according to this theory, feel no obligation to keep his word. We believe, on the contrary, that moral obligation is felt by the atheist, and that he cannot divest himself of it. When men are tempted by some strong motive to deviate from the truth, and yet are enabled to resist the temptation, there is in most cases no distinct consideration of any future good to be gained by it, but the man feels himself under an obligation to do that

The true doctrine is, that virtue and vice are distinct and opposite, and that when we know any act to be right, we are bound-apart from all considerations of self-interest-to perform it.

Dr. Paley maintains that "we can be obliged to do nothing, unless we are to lose or gain something by it, for nothing else can be a violent motive' to us. And as we should not be obliged to obey the laws or the magistrate, unless rewards or punishments, pleasure or pain, somehow or other depended on our obedience; so neither should we, without the same reason, be obliged to do what is right, to practise virtue, or to obey the command of God."

According to this view, unless a man is persuaded that he shall gain something by keeping his word, he is under no obligation to do it. Even if God should clearly make known his will, and lay upon him his command, he is under no obligation to obey, unless certain that he shall receive benefit by so doing. This is, indeed, to make virtue a mercenary thing, and reduce all motives to a level. And as self-love, or the desire of happiness, is the only rational motive, and all men possess this in a sufficient degree of strength, the only conceivable difference between the good and the bad consists in the superior sagacity which the one has above the other to discern what will most contribute to happiness. And if what we call vice or sin could be made to contribute to happiness, then it would change its nature and become virtue.

The definition of obligation, given by Dr. Paley, upon his own principles, is unnecessarily encumbered with what adds nothing to its import. Why should the "violent motive" result from the command of another? The command of another ought to have no influence, except as obedience or disobedience will be attended with loss or gain. It would, therefore, have been more simple and intelligible to say at once, what is certainly implied, that the only motive which can oblige us to be virtuous, is the expectation of the happiness to be derived from such conduct in the future world.

who confounded the honestum with the utile, deserve to be Cicero, in his work "De Finibus," says that those men banished from society. The result of the whole scheme is, that there is no such thing as moral excellence, abstractedly considered; that the only good in the universe is happiness; and that other things, among which virtue is included, are good only as related to this end. If this is true, the moral attributes of God have no intrinsic excellence; they are all merged in his infinite felicity. Surely this view is not suited to increase our reverence for the Supreme Being.

But every man who carefully examines into his own primary ideas of morality, will find that he has a sense of right and wrong, independent of all considerations of personal happiness, or its loss. This distinction is too deeply engraven on the mind to be erased by any process of reasoning.

THE SUPREMACY OF CONSCIENCE.

That the dictates of conscience should be obeyed, is one of the most evident convictions of the human mind. No matter how much might be gained by going contrary to conscience, every honest mind has the same judgment, that duty should be done. If it is plain that a certain act-such as confessing the truth of the gospel-is a duty, and we are convinced that nothing but suffering will ensue from performing it; yet the loss can ever justify us in denying the truth, or in doing any judgment of the impartial mind is, that no prospect of pain or thing else that we know to be wrong. On this point there is no room for reasoning, The judgment that conscience should be obeyed is intuitive: all men must acknowledge it, unless they belie the clear convictions of their own reason.

performed at every risk, are maxims which must receive That conscience should be obeyed, that duty should be the assent of all who are capable of understanding them. On