ページの画像
PDF
ePub

fear of punishment, or to be excited by the feelings of ingenuous temper; can be known only to the searcher of all hearts. In human governments, appearances may be decisive, while the heart is not the least touched: It would, therefore, be the height of absurdity, that sorrow should make atonement for offences, when we know not whether that sorrow be genuine or not.

But if contrition, allowing it to be sincere, for breaking the laws of any government be sufficient to avert the stroke of justice, it would be proper, in such case, for the writer to apprise the subjects of it by an open declaration, that, whosoever shall be guilty of any offence shall be pardoned if he does but repent." Now, who does not see that this would be giving licence to men to break the laws as often as they pleased, and that such conduct would overthrow every government human and divine?

"The only effect sorrow for a crime can ever produce, is reformation, and a return to obedience: but this, in the very nature of things, can never be an atonement for past offences; it may indeed prevent the commission of more crimes, but cannot be any satisfaction for those already perpetrated. A person who has plunged himself into debt may be and often is extremely sorry for it, and possibly may avoid extravagance for the future, but surely, gentlemen, his sorrow and subsequent oeconomy will never pay off his old debts, or satisfy the demands of his creditors."

"The utmost contrition that can be experienced is no compensation for a private injury, much less for a public offence. In the case of a man robbed or murdered, whose wretched orphans are thrown upon the mercy of the world, will it be said that the keenest pangs of sorrow the criminal can feel, will afford any satisfaction to the hopeless children? Certainly not. The punishment of vice is a debt eternally due to public justice, which can be cancelled only by the sufferings of the offender, or an equivalent accepted by a sovereign whose laws are broken."

:

'In human governments, the power of dispensing with the laws in particular cases, is universally acknowledged to arise from the weakness and imperfection of all human systems. It is properly remarked by Marquis Beccaria, on Crimes and Punishments, that a perfect legislation excludes the idea of pardoning, or suspending the stroke of justice and as the divine laws must necessarily be perfect (being the result of infinite wisdom) it clearly follows, there can be no such thing as a complete and total remission of the penalty where they are broken. Either the offender himself must suffer the penalty, or some other person, as a substitute: and there can be no reason why a Sovereign may not accept the vicarious sufferings of a substitute, provided the infliction of the punishment upon him will answer the great end of public justice, support the rights of government, and deter others from disobedience to

the law."

"Both human and divine laws require suffering as the only atonement for transgressing them. The ideas of guilt and suffering, are indissolubly associated in the human heart. The practice of all nations corroborates the reasoning now advanced; for in all ages and countries mankind have had recourse to sacrifices, in order to appease the Deity by the vicarious sufferings and blood of victims. An unequivocal proof, that the voice of nature has uniformly demanded sufferings as the proper VOL. II.

U

atone

atonement of guilt, and that sorrow alone is not a sufficient expiation. pp. 23-27.

The subjects introduced in this volume are common, but highly important; they are of a nature to require and to reward repeated consideration. But as a frequent recurrence of the same remarks is found generally to disgust rather than to impress us, it is very desirable that an author should possess the talent of engaging that regard by the manner of his discussions, which the subject itself may have ceased to excite. To this praise we think Mr. Rush is fully intitled; and we cordially recommend his useful performance to the attention and patronage of the public. The work is, in general, correctly as well as neatly printed; however, Sir Richard Steele is, erroneously called Sir Robert.

Art. IX. Leslie's Inquiry into the Nature &c. of Heat.

[Concluded from p. 189.]

WE proceed to consider the author's application of his principles, to explain the phænomena which his numerous and well-devised experiments have elicited.

It is necessary, first, to give some idea of the Construction of the instruments which were employed. These were block-tin mirrors from twelve to about fourteen inches in diameter, and with a depth of concavity from 1 to near 2 inches; blocktin hollow tubes or canisters of different sizes, of three, four, six and ten inches; one side of which was kept clean and bright, the opposite side was covered with writing paper, or painted over with lampblack, the other sides being allotted for miscellaneous service. With these was employed a sort of thermometer, than which Mr. Leslie remarks, nothing could be more simple or commodious. In this opinion we fully concur; the philosophical world is considerably obliged to Mr. Leslie for the invention of this singularly delicate measure of heat. It is thus constructed.

Two glass tubes of unequal lengths, each terminating in a hollow ball and having their bores somewhat widened at the other ends, a small portion of sulphuric acid tinged with carmine being introduced into the ball of the longer tube, are joined together by the means of a blow-pipe, and afterwards bent into nearly the shape of the letter U, the one flexure being made just below the joining, where the small cavity facilitates the adjustment of the instrument, which, by a little dexterity, is performed by forcing with the heat of the hand a few minute globules of air from the one ball into the other. The balls are blown as equal as the eye can judge, and from four-tenths to seven-tenths of an inch in diameter. The tubes are such as are drawn for mercurial thermometers, only with wider bores; that of the short one, and to which the scale is affixed, must have an exact calibre of a fiftieth or a sixtieth of an inch; the bore of the long tube need not be so regular, but should be visibly larger, as the coloured liquor

liquor will then move quicker under any impression. Each leg of the instrument is from three to six inches in height, and the balls are from two to four inches apart. The lower portion of the syphon is cemented at its middle to a slender wooden pillar inserted into a round or square bottom, and such that the balls stand on a level with the centre of the speculum. A moment's attention to the construction of this instrument will satisfy us that it is affected only by the difference of heat in the corresponding balls, and is calculated to measure such difference with pecu liar nicety. As long as both balls are of the same temperature, whatever this may be, the air contained in the one will have the same elasticity as that in the other, and consequently the intercluded coloured liquor, being thus pressed equally in opposite directions, must remain stationary. But if, for instance, the ball which holds a portion of the liquor be warmer than the other, the superior elasticity of the confined air will drive it forwards, and make it rise in the opposite branch above the zero, to an elevation proportional to the excess of elasticity or of heat. The interval between freezing and boiling water being distinguished into an hundred equal parts, called centigrade, each of these subdivided decimally constitute the degrees which I employ, and which, following up the same system of nomenclature, would be termed milligrade.' pp.9—1 L.

The canister being placed on a table, a few feet distant from the reflector, with its papered or blackened side directly fronting it, and the place of the corresponding focus being found by a lighter taper; the ball of the differential thermometer, called the focal ball, is moved to that spot, the plane of the instrument being parallel to the face of the reflector. On filling the canister with boiling water, the coloured liquor of the thermometer was seen to rise; in the space of two or three minutes it had mounted to nearly the top of the scale, and having remained a short time stationary, it slowly descended as the canister cooled. Mr. L. found this effect, in every case, exactly proportionate to the heat of the canister, or the difference of its temperature from that of the room. The experiment was found to succeed equally well with cold as with heat, for the canister being filled with ice, or with a frigorific mixture, the focal ball was chilled, and the coloured liquor consequently sunk: the effect, though in a contrary direction, being still rigorously proportional to the difference of temperature. Hence it appeared unquestionable, as Mr. Leslie observes, that some hot or cold matter actually flowed from the canister towards the reflector, and from the reflector to the focal ball.

The experiment was repeated with the following changes and results. The black side of the canister filled with boiling water being turned to the reflector, the liquor of the differential thermometer rose to 100; another side covered with paper being thus disposed produced an effect equal to 98°; another side covered with a pane of crown-glass, produced an effect only equal to about 90°; and the bright side of the canister being brought to face the reflector, the coloured liquor quickly sunk

to

to 12°. To produce this latter effect, it is only necessary to employ any clean metallic surface. These are the chief differences which respect the canisters.

With regard to the difference of the reflectors:-A concave mirror being employed instead of the tin reflector, the liquor rose through a small but visible space, nor was this effect increased by rubbing off the silvering from the mirror, nor by grinding its hinder surface. By coating it with Indian ink, the effect became altogether invisible, and by covering the face of the mirror with a sheet of tin-foil closely adapted to its surface, an effect was produced which exceeded ten times that of the naked mirror.

Mr. L. now advances with confidence, and seems to anticipate the triumph of his theory.

The facts related in this chapter will be deemed at least very curious; and viewed all together, they are calculated, I think, to affect us with surprize. Nay, they are repugnant to our first notions, and might experience contradiction, if they were not so easily verified.'

The power of absorbing heat, and the power of emitting it, seem always conjoined in the same degree; and this uniform conjunction clearly betrays a common origin, and discovers the evolution of a single fact, which assumes contrary but correlative aspects.-In the reflecting of heat also, we readily perceive that the very different aptitudes exhibited by different surfaces are derived from the same principle. portion of heat only is reflected which has not been previously absorbed. Thus a coat of china ink affords no reflection perceptible because it is 'most absorbent of heat.'

That

Whatever reasonings are employed concerning the operations of Heat, the same must, with equal propriety, apply to those of Cold.'

'Do not both of them produce their distant effects by the agency of the same individual fluid, susceptible, like all matter, of every possible degree of temperature ? pp. 23-25.

Various experiments are next described in which different substances were interposed as screens between the canister and reflector, the blackened surface of the canister being presented, -and the screen being placed about two inches from it. A sheet of tinfoil thus disposed appeared completely to intercept the effect upon the focal ball; and the same power was found to be possessed by gold leaf: manifesting that there is an actual flow or impulsion of some corporeal substance. A pane of crown glass being substituted for the tinfoil, the thermometer rose to 20°, being one fifth of the intensity manifested when nothing. was interposed. This experiment impels Mr. Leslie to the consideration-Has the fluid which is thrown from the canister any relation to light? In resolving this question Mr. Leslie reminds us that, although light permeates glass and other diaphanous substances, it yet suffers in its passage a certain degree of diminution or absorption; and that, whether light passes in a

condensed

condensed or in a diffused state, it must, in either case, sustain the same proportional loss; because each particle travelling through the same range of matter, must incur the same risk of impediment. Here, then, Mr. Leslie thinks is a simple criterion by which to decide, whether the fluid, which is emitted from the heated surface, really penetrates through the glass, and thence emerging with diminished quantity, continues its course; since it would experience the same measure of absorption, four fifths of the whole, in whatever part of its transit, from the canister to the reflector, it encountered the screen. The pane of glass was therefore successively carried forwards, the effect on the focal ball proportionally diminishing, and, when it was advanced a foot before the canister, not exceeding the thirtieth part of the full effect. Hence Mr. Leslie concludes that the fluid thrown from the canister is not, like light, capable of permeating glass. A sheet of writing paper being substituted for the glass at the original distance of two inches from the canister, an effect was produced nearly equal to the fourth part of that which was produced without the screen.

The following experiment being considered by Mr. Leslie as particularly illustrative of his opinion, we deliver it at length, together with the inference which he deduces from it.

'Select two panes of crown-glass as flat and smooth as possible, and coat one side of each with tinfoil, by means of a little gum-water. Thus prepared, and the apparatus put in order, join those panes together with their tin surfaces in contact, and attach them to the frame of the screen; the focal ball will receive an impression equal to about 18 degrees. Invert the panes of glass, placing them with the tin coatings outmost: the liquor of the differential thermometer will now sink back again to the beginning of the scale.

Such is the experimentum crucis. It establishes beautifully and, I think, beyond the power of contradiction, the simple theory to which we have been led by a close train of induction, In both cases the obstacle presented, or the compound screen, is absolutely the same. If the effects in the focus of the reflector were produced by some subtle emanation capable of permeating solid substances, how could such a singular contrast obtain? It seems impossible to elude the force of this argument.'

pp. 35-36.

Admiring, as we do, the excellence and simplicity of Mr. Leslie's apparatus, the felicity of his experiments, and the acuteness of his reasoning, we are yet unable to admit all the points of his theory. Indeed when we reflect on the general adoption which his theory has experienced, and the high authority by which it has been sanctioned, we venture not without reluctance to entertain a suspicion of its solidity. But the sixth and seventh experiments have excited doubts, which we have not been able to remove. Nothing offered by Mr. Leslie satisfactorily explains to us, how such a difference could have arisen, as that which

« 前へ次へ »