ON PHYSICS, OR NATURAL PHILOSOPHY.

No. LIX.

(Continued from page 494.)

that is to say, bring it back to the natural state in two ways, by a slow or an instantaneous discharge. To discharge it slowly, first touch the plate A-that is, the plate which contains an excess of electricity-with the finger, then all the positive fluid which is not made latent by the negative fluid of the

BOTH ELECTRICITIES.

Latent Electricity; Condenser.-Latent electricity is the state of neutralisation presented by the two electric fluids when, being brought together on the surfaces of two conducting bodies, they are separated by only a thin non-conducting layer. Through this neutralisation the electric charge may become very considerable, and greatly surpass what would take place in a single body. The apparatus by which electricity is thus accumulated is called a condenser. There are various sorts of condensers, all based upon the principle of electrisation by influence, and consisting of two conducting bodies separated by a non-conducting body.

399.

The condenser of Epinus is formed of two circular copper plates ▲ and c, and a glass plate в which separates them, fig. These plates being each furnished with an electric pendulum having a conducting rod, are isolated by glass feet, capable of sliding along a groove in the stand upon which they are placed. They are thus brought near to each other or separated to any distance that may be required. To collect the two electricities on the copper plates, put them in contact with the glass plate, as in fig. 398, then by means of

Fig. 398.

latent a quantity of electricity less than its own, it is the plate c which after this first contact possesses the strongest charge; in fact, we see that the pendulum a falls back and the pendulum c diverges. If we now touch the disc c, its pendulum falls back while the pendulum a diverges, and so on if we continue touching the two discs alternately. The discharge takes place only very slowly, and if the air is dry, it is not completed until several hours have elapsed. If you first touched the plate c, which is less electrised, you would not remove any electricity from it, because all that it contains is rendered latent by the disc A.

When we wish to discharge the conductor instantaneously, we bring the two plates into communication by means of the exciter, an instrument consisting of two brass arcs with a ball of the same metal at the end of each, and connected together by a hinge upon which they turn. When the instrument is furnished with glass isolating handles, as in fig. 400, it is called the glass-handled exciter; if there are no handles, it is called the simple exciter. To make use of the exciter, apply one of the balls to one of the plates of the condenser, and bring the other near the second plate. A strong spark then appears, arising from the recombination of the contrary electricities Fig. 399.

metallic chains make one of them, as e. g. A, communicate with an electrical machine and the other with the earth. The disc A is then electrised positively, like the machine, and if it were alone it would have the same quantity of electricity on an equal surface, allowing for the influence of the form; but the disc c completely changes the phenomenon, and it is that which causes the accumulation of the two electricities. In fact, the positive fluid of the disc a acting by influence through the glass on the plate c, attracts the negative fluid and repels the positive fluid into the earth. Now the negative fluid of the disc c reacts in its turn upon the positive fluid of the disc A and neutralises it, but only partially, on account of the interval between them. The electric tension on the disc A is no longer in equilibrium with the tension of the machine: the consequence of which is, that this latter communicates to the plate a fresh quantity of positive fluid, which acts as before upon the disc c, and so on up to a certain limit.

Slow and Instantaneous Discharge.-When the condenser is charged, that is to say, when the contrary electricities are accumulated on the two surfaces, the communication with the electrical machine and with the ground is broken by removing the two metallic chains. Only a part of the electricity of the plate A is then latent, while that of c is completely so. In fact the pendulum a diverges, while the pendulum c is vertical. But if we remove the plates from each other, fig. 399, both pendulums diverge, for the electricities are no longer latent. The plates being in contact with the isolating plate, fig. 398, and the chains removed, we may discharge the condenser,

VOL. V.

accumulated on the two surfaces of the condenser. The recombination, however, is not complete, for we may in the same manner elicit a second and a third spark, and even more, though they become more and more feeble. Hence it is inferred, that when the two plates communicate together, the two electricities cannot be entirely recombined. On discharging the condenser with the exciter, we feel no sensation though we hold the exciter in the hand, and though it be the simple exciter. This

Fig. 400.

is owing to the fact, that the electric fluid always choosing electricities is effected by the metallic arc, and not by the body of the experimenter. But if, while touching one of the

the best of two conductors, the recombination of the two

137

Leyden jar consists of a thin glass bottle, varying in size according to the quantity of electricity which is required to be collected. The inside is filled with gold or copper leaf. The outside and the bottom are covered with tin-foil B, which, however, terminates at a considerable distance from the neck of the bottle. Through the cork passes a copper rod bent into a hook, and terminating in a knob A. Inside, this rod communicates with the gold or copper leaf which fills the bottle, and is called the internal armature, the tin-foil в being called the external armature.

The Leyden jar is charged, like the condenser of pinus and the fulminating square, by making one of the armatures communicate with the earth and the other with the electric source. For this purpose, hold it in the hand by the external armature, and present the internal armature to an electrical machine, the positive fluid then collects on the gold leaf, and the negative upon the tin-foil. The contrary would take place if, while holding the jar by the hook, you were to present the external armature to the machine. The theory of the Leyden jar is the same as that of the condenser. Like the condenser, it is discharged slowly or instantaneously. To discharge it instantaneously, hold it as in fig. 405, and bring the two

Fig. 405.

armatures into communication by means of the simple exciter, taking care first to touch the armature held in the hand, otherwise a shock will be felt. To discharge it slowly, isolate it on a cake of resin, and touch, first the internal armature, with the finger or a metal rod, and then the external armature, and so on continually, eliciting each time a feeble spark. To render the slow discharge more perceptible, arrange the Leyden jar as represented in fig. 406. The rod is straight and furnished with a small bell. Near the jar is a metallic rod with a second bell like the first, and a small electric pendulum consisting of a copper ball attached to a silk thread. The jar not being fixed to the board в on which it is placed, take hold of it by the external armature and charge it by bringing it near an electrical machine, and then put it on the board. The internal armature now containing an excess of positive electricity not neutralised, the pendulum is attracted and knocks the bell of the jar. It is then repelled immediately, and goes to the second bell, to which it communicates its electricity. But on returning to a neutral state it is again attracted by the first bell, and so on for several hours, if the air is dry and the jar large.

which are capable of separation, consists of a large conical glass vessel B, fig. 407, an external armature c of tin plate, and an internal armature D of the same material. These portions being placed one in the other, as represented in fig. A, form a complete Leyden jar. After having electrised it, like the common jar, and isolated it on a cake of resin, fig. A, remove the internal armature with the hand, then the glass vessel, and lastly the external armature, and arrange them all in a row as represented in the figure. Now the two armatures are evidently thus brought to the natural state. But if you put back the armature c on the cake of resin, and put the glass vessel in it, and again the armature D in this, you again form a Leyden jar, which gives a spark almost as strong as if you had not discharged the two armatures. Hence we infer that the two latent electricities, yielding to their mutual attraction, leave the two armatures in a great measure and go to the surfaces of the glass.

Cascade Charge.-This name is given to an electric charge which is transmitted from one Leyden jar to another, when they are arranged one above another as follows. The first is attached by its hook to the conductor of an electrical machine, then the hook of the second passes through a metallic ring fastened to the external armature of the first; a third is attached to the second in the same manner, and so on to the number of five or six, the external armature of the last communicating with the earth by a metallic wire. As soon as the first jar is charged, it reacts upon the neutral fluid of the second and decomposes it, then this reacts in the same way upon the neutral fluid of the third, and so on throughout till all the jars have the same fluid as the machine, and the contrary at their external armatures. These jars can be discharged one after the other, or all together, by making the internal armature of the first communicate with the external armature of the last.

Electric Jars and Batteries.-An electric jar is a large Leyden

is to consider habits and habitual actions as they partake of a moral character, or as they are the object of moral approbation or disapprobation. If we should remove from the list of moral actions all those which are prompted by habit, we should cut off the larger number of those which men have agreed in judging to be of a moral nature.

That there are virtuous habits and vicious habits, will scarcely be denied by any considerate person. A habit of lying, of swearing, of slandering, of cheating, of irreverence, of indolence, of vainglory, with many others, are, alas! too common. There are also virtuous habits, such as of industry, temperance, kindness, veracity, diligence, honesty, etc. To be sure, these virtues commonly flow from principle, but the practice of them is greatly facilitated by correct habits. Two considerations will show that men are properly accountable for those actions which proceed from habit. The first is, that in the formation of his habits man is voluntary. The acts by which they are formed are free acts, and the agent is responsible for all their consequences. The other consideration is, that habits may be counteracted and even changed by the force of virtuous resolutions and perseverance. Where habit has become inveterate, it may be difficult to oppose or eradicate it; but the strength of moral principle has often been found sufficient to counteract the most confirmed habits. When it is asserted that men long enslaved by evil habits cannot make a change, it is on the ground that no principle of sufficient power exists in the mind of the agent; but for that deficiency the man is responsible. Yet a power from without may introduce a new principle potent enough to overcome evil habits. The importance of possessing good habits is admitted by all moralists. Aristotle makes the essence of virtue to consist in "practical habits, voluntary in their origin," and agreeable to right reason. Dr. Thomas Reid, in his "Essay on the Active Powers," defines virtue to be "the fixed purpose to act according to a sense of duty," which definition Dugald Stewart modifies, by observing, "It is the fixed purpose to do what is right, which evidently constitutes what we call a virtuous disposition. But it appears to me that virtue, considered as an attribute of character, is more properly defined by the habit which the fixed purpose gradually forms than by the fixed purpose itself." Dr. Paley lays it down as an aphorism, that "mankind act more from habit than reflection." "We are," says he, "for the most part, determined at once, and by an impulse which has the effect and energy of a pre-established habit." To the objection, "If we are in so great a degree passive under our habits, where is the exercise of virtue, or the guilt of vice?" he answers, "in the forming and contracting of these habits." "And hence," says he, "results a rule of considerable importance, viz. that many things are to be done and abstained from solely for the sake of habit."

THE NATURE OF VIRTUE.

The theories on this subject have been numerous, and contrary to one another. It is now proposed to mention some of the principal of them. We shall first mention the theory of Mr. Hobbes and his followers, who deny that there is any natural distinction between virtue and vice, and maintain that by nature all actions are indifferent, and that our ideas and feelings on the subject of morality are altogether the effect of education and association. Mr. Hobbes did indeed maintain that men are bound to obey the civil government under which they may happen to live, and to conform to the religion established by law, however contrary to their own private judgment. All moral duty, according to this theory, was resolved into the authority of the law of the land. As no natural moral rule existed, it was held that, except so far as a man was restrained by civil authority, he had a right to do what he pleased; and while he confined himself within these bounds, he need feel no concern about the consequences of his conduct.

Perhaps the most extraordinary system of virtue every promulgated was that of Mandeville, who maintained that all pretensions to virtue were mere hypocrisy, which men assumed from the love of praise. This writer forgot that hypocrisy assumes it as true that that which is counterfeited is an object of esteem and approbation among men. That virtue consists in the mere pursuit of pleasure, or of our own interest, is a system as old as Epicurus, and has had many abettors up to this time.

But the whole plausibility of their arguments depends on the pre-established connexion between happiness and a virtuous course of life. That true happiness is the natural effect of virtue, falls entirely short of proving that the essence of virtue consists in the tendency of certain actions to the person's true interest; whereas, when we perceive an action to be virtuous, we are conscious that it is not from any view of the connexion of the action with our own happiness that we approve of it; but our judgment is immediate, founded on a moral character perceived in the act itself. And in many cases virtue requires us to deny ourselves personal gratification for the sake of others. A man supremely governed by a regard to his own interest, is never esteemed a virtuous man by the impartial judgment of mankind. According to this theory, the only thing censurable in the greatest crimes is, that the guilty person has mistaken the best method of promoting his own happiness. Upon this principle, a man is at liberty to pursue his own interest at the expense of the happiness of thousands, and if he is persuaded that any action will tend to his own interest, he is at liberty to do it, whatever may be the consequences to others.

Dr. Paley adopts the principle that all virtue consists in a regard to our own happiness, taking into view the whole of our existence. His definition is, however, a very complicated one, and deserves to be analysed.

Virtue," says he, "is the doing good to mankind, in obedience to the will of God, for the sake of everlasting happiness," according to which definition the good of mankind is the object, the will of God the rule, and everlasting happiness the motive of human virtue. If the question be asked, why we should seek the good of mankind, the answer is, from a regard to our everlasting happiness; and if the question be, why should we make the will of God the rule of our conduct, the answer must be the same; so that really all virtue is resolved into a regard to our own happiness.

Now every man desires to promote his own happiness, and according to Dr. Paley's theory, the only difference between an eminently good man and one of the opposite character is, that the one pursues a wiser course than the other; but they are both actuated by the same motives.

This theory loses sight of all intrinsic difference between moral good and evil, and admits the principle that happiness is the only conceivable good, and that anything is virtuous the tendency of which is to promote our greatest happiness.

A theory the opposite of that which makes a regard to private interest the ground of virtue, is the one which makes all virtue to consist in a regard to the public good. This is the theory of Bishop Cumberland in his work, De Legibus, and is not essentially different from the scheme of those who make all virtue to consist in disinterested benevolence. No doubt, much that deserves the name of virtue consists in good will to others, and in contributing to their welfare; but it is not correct to confine all virtuous actions to the exercise of benevolence. We can conceive of benevolence in a being who has no moral constitution. Something of this kind is observable in brute animals, and atheists may exercise benevolence to their friends. The indiscriminate exercise of benevolence to creatures, without any respect to their moral character, might appear to be an amiable attribute, but it could not properly be called a moral attribute. A prudent regard to our own welfare and happiness is undoubtedly a virtue. It has been considered so by the wisest of men, and we know that prudence was one of the four cardinal virtues of the heathen. As the whole is made up of parts, it is evident that if it is a virtue to promote the well-being of the whole, it must be so of each of the parts. The pursuit of our own happiness where it does not infringe on the rights of others, has nothing evil in it, but is approved by every impartial mind. Some who maintain that all virtue consists in benevolence, admit that we may seek our own happiness just as we seek that of our neighbour; but the human constitution is not formed to exercise that abstract impartiality. While we are bound to promote the welfare of our neighbour and of strangers, our obligation is still stronger to endeavour to secure our own happiness; and if a friend and a stranger stand in equal need of a benefit which we have it in our power to bestow, it is evidently our duty to consult first the welfare of our friend, other things being equal.

What Bishop Butler has said on this subject in his short treatise on "Virtue," is worthy of consideration: "It deserves