bing it off till nothing is visible, and breathing on it again, the spectrum of the penny appears, as well as of the fourpenny piece, proving that dust adheres much more strongly than we should have supposed, or perhaps better-leaves its mark with much greater pertinacity. That this is the true explanation of the appearance of a spectrum, when the coin is not in direct contact with glass, was to me rendered clear by another experiment, in which a halfcrown was left on one sixpence, and a penny on another, on a clean glass plate covered over with paper, and kept in a closet for ninety-six hours; yet on examination, neither a permanent spectrum, nor even an evanescent one by breathing, was perceptible either of the half-crown or the penny; the sixpences alone had left spectra, (which, however, were only visible by breathing), that under the half-crown being the clearest. Yet the penny and half-crown were in the best condition for giving spectra, for the surfaces of both were tarnished, and that of the copper purposely so. plan. But even at this distance I have not succeeded, if the half-crown laid on the fourpenny piece is perfectly polished, and all external dust, fc., carefully excluded by the box just mentioned-(see Sec. 8, on the comparative polish of metals.) 6. As regards impressions on glass.-We have already observed that heat does not seem to increase the effect of metal coins on glass. Neither did long contact; for a fourpenny piece, left a week on a piece of looking-glass, only left the usual spectrum, no figure being visible. The same remark applies to large printed letters. At least, some paper with these, after remaining pressed two or three days without giving any impression, was then heated for five hours, so pressed, at about 160°, but no impression was made. On another occasion, print and writing were left a week on a glass mirror without leav ing an impression. When, however, thinner paper and larger letters were used, and heat and pressure applied as above for four or five hours, these letters were plainly visible; but, as This result induced me to try the same with a appeared to me, far more easily erased than copper plate, and I found that when a bright were the spectra of coins on copper plates.* A half-crown (having been well boiled in water slight touch of the finger, for instance, erased and then polished) was placed on a fourpenny the letters in question. They were produced in piece, similarly treated, and left forty-eight hours this case in consequence, no doubt, of the thincovered in the closet, as above, that the half-cer paper being moister than that first used. crown left no spectrum, even evanescent. Neither did a purposely tarnished penny placed on another fourpenny piece, and left the same time. 5. As regards the distance from the plate at On putting a penny on a sovereign, and leavwhich images may be taken.—A silver fourpenny ing them for three hours and a half at the above piece is about the one-twentieth of an inch in heat, I thought the spectrum of the penny slightthickness, and at this distance we have seen sil-ly visible; but as the image is never so apparent ver, copper, and of course gold, give a spectral as on polished metal, I shall not venture a deimage on a copper plate. But on putting a half cided opinion on this point as regards glass. crown on two sixpences and a half-frank piece, A polished, boiled, and then well dried halfmaking the distance from the plate more than crown gave as good a spectrum on a glass plate the one-tenth of an inch, no spectrum of the half-in twenty-four hours, as did a dirty half-crown; crown was made, although the experiment was but I thought the spectrum of the former disapcontinued for twelve successive days and nights. peared sooner by breathing. On a far thinner Neither was any made by removing the half-glass plate, a bright, boiled fourpenny piece, left franc piece (thus making the distance only one- the same time, gave no spectrum at all. tenth of an inch), and continuing heat of 160° or so for five hours. A sovereign fixed at three quarters of an inch, and a small brass medal at somewhat less than half an inch, from a polished copper plate, and continued in such position for seventeen days and nights in a little closed deal box, gave not the least vestiges of spectra; neither did a fourpenny piece left at one-fifth of an inch, nor a card plate (engraved) left the one-tenth of an inch, for eleven days. The copper plate had remained perfectly polished in both experiments; and this is worthy of remark, as showing that in confined air copper does not oxidate perceptibly. Another plate left in the same room was completely tarnished in five or six days. A fourpenny piece, about the one-twentieth of an inch, under a silver plate for eleven days, gave scarcely a perceptible spectrum; though a farthing, on which the plate had rested, gave a good spectrum, but not a permanent one, (i. e. breathing was required to show it). A fourpenny piece is about the one-twentieth of an inch in thickness, and this seems the greatest distance an image can be taken by the above Heat does not appear to increase the effect on glass. A fourpenny piece under a shilling for three hours, at 160°, left no spectrum. 7. Polished surfaces not appearing capable of receiving the impressions. These exceptions from the general rule I have found to be talc, and, among the metals tried, steel to a certain extent, platinum, and gold. Whether heated or not with the coins on it, I have found no spectrum produced on talc, except in one instance, where a tarnished half-sovereign had been pressed some days by a half pound; and even here the mere margin of the coin was barely perceptible.† On steel, after remaining twenty-four hours, I * On a copper plate also this thin paper (not being dried well first) gave a permanent and very visible spectrum, the lettering being clearer than on glass not due to oxidation, for on rubbing it off, the surface of the copper was left polished-i. e. oxidation, in the usual sense of the term: for there, no doubt, was some very slight chemical action, as large printed letters on perfectly well dried paper were not taken off on a copper plate, the heat at 1609 being applied for five hours; or on another occasion, the print remaining a week on the plate, and pressure being used. acid. Talc, like platinum, is not easily acted on by found a very slight evanescent spectrum produced by a small piece of brass, and on one occasion by a half-sovereign very much tarnished; but as heat did not appear to increase or hasten the effect, we may consider steel as almost unsuspectible. The spectra just named disappeared entirely after breathing twice; and no permanent spectrum was produced, though the piece of brass above mentioned was placed even on the top bar of a grate, and of course kept very hot for two or three hours. Under the head "Thinness of the plates," experiments, showing the incapability of platinum to receive images, are mentioned. The same remark applies also to gold. I kept a shilling and a farthing, on two different occasions, for twenty-four hours or longer on a well polished plate of gold, yet they barely left a marginal spectrum; and this spectrum, as in the case of steel, disappeared entirely on breathing on it twice. As the gold used was not free from the usual alloy of copper, possibly this was the cause of its receiving even the very slight spectrum it did. However this be, these experiments seem almost sufficient to establish the important general principle-viz., that the less metals are oxidable by exposure to the air, the less is their susceptibility to receive spectra. and also this was the case with that of the most 9. Which metal receives images fastest, cop copper, whether heat be applied or not. When the same degree of heat was applied, I found a sovereign produced a good permanent spectrum (impression) on a bright copper plate, although only an evanescent one (one seen only when the plate is breathed on) was produced on an equally well polished silver plate, placed at the same time at the same heat. When heat was not applied I found the copper received fan evanescent spectrum first. 8. As regards comparative polish in metals.1. A new sovereign, a new half-crown, and new farthing (all well polished) were kept on a bright copper plate, at 160° or above, on two successive occasions, for four or five hours. The gold and silver left only very slight permanent traces of their margin, the copper left none at all, but its spectrum, when the plate was breathed on, be-per or silver?-My experiments lead me to say came, I thought, even rather more evident than the spectra of the gold and silver, these being likewise breathed on. 2. A tarnished sovereign and a tarnished half-crown being laid on the same copper plate, and kept at the same heat only three-quarters of an hour, a permanent, and far more apparent, spectrum was produced than in the former case; the whole era, where the half-crown had laid, was covered with a whitish cloud, and the impression dimly sketched. 3. By selecting a half-penny very much tar- 10. As regards the effect of interposed subnished, and letting it remain five hours on a stances.-As every substance tried left a specbright copper plate, heated to 160° or so, and trum, I did not much expect that the influence subsequently for thirty-six hours in the cool, a would permeate any lamina, even of the thinpermanent spectrum was produced, in which all nest description. Accordingly, when a sovethe lettering of the coin was beautifully visible; reign or shilling was left twenty-four or fortyyet here was copper on copper. But as I found eight hours on a piece of stiff, though very thin, this impression to go off completely at a heat paper, it gave no spectrum, but the mark of the far below what the impression did, at exp. 5, be-paper was alone visible. The experiment was low, the general principle, that silver gives a repeated, half the coin resting on the copper stronger impression, remains. 4. A well pol-plate and half on the paper: and although it reished new sovereign and a tarnished sixpence mained a fortnight in this position, the half only being laid on a bright silver plate for four hours, in contact with the plate was visible by breathand kept at 160°, the sovereign had left no ing o the paper, leaving its own spectral image spectrum, but the sixpence had left a permanent just as if no coin had rested on it at all. one, in which almost all the lettering appeared, so plainly was it visible. 5. A perfectly polished half-crown was laid on a pretty-well polished sixpence, and a purposely tarnished one on a purposely tarnished sixpence, and put on the With the glass the experiment was only consame plate with the half-penny (exp. 3, above), tinued forty-eight hours; with the paper, tale, and heated five hours and left thirty-six hours after-cork, a fortnight, silver coin being used; with the wards. The lettering, &c., of each sixpence whalebone and gum, ten days, gold coin being was visible, but far more of the most tarnished; used. The same experiment was repeated with the thinnest possible layers of talc, gum, cork, and whalebone, glass, plane and concave, with the same result. Each substance left its spectrum, the part where the coin rested on such layer not | a highly polished lamina of steel,-heated to being at all distinguishable. The spectral image of the square piece of talc was perfect to the minutest outline, and left its straight mark under the sixpence equally well as at other points. These experiments render it clear that the effect is not due to latent light, for other wise how could it happen that a coin does not leave a spectral image when left on transparent substances, glass or talc, even a fortnight? They also show it does not depend on heat (at least alone), for a heat of 160° soon passed through thin glass and talc, and I found it impossible to keep my finger on glass or talc so placed. Yet we have seen above that even gold left two hours on talc so heated left no spectrum, permanent or temporary. So great is the effect of interposed substances, that even a slight tarnish on the metal exerts a very obvious effect.* One shilling was left twenty-four hours on a polished The result of this experiment obviously part of the plate, and another on a part of the shows, that although thinness and elasticity same slightly tarnished (but yet sufficiently may have some little effect, the principal cause bright to see one's self perfectly). A very slight for the formation of the spectrum is the peculiar image only was left in the last case, that en-chemical nature of the metal, and that a spectirely disappeared when breathed on twice, trum cannot be produced on a non-oxidable while that on the polished part of the plate re. metal, such as platinum. Bright silver and copmained, after being breathed on twelve or four- per plates are well known to tarnish by exposure to the atmosphere (the former, perhaps, rather by forming a sulphuret than an oxide), but no matter how. I have also found that spectra could be formed on tin and zinc plates, both of which, of course, are oxidable. So on copper coated with mercury, the mercury in such case no doubt readily tarnishing (see section 7, polished surfaces not receiving spectra). Having decided that the effect in question is due neither to light nor heat, to what cause, it may be asked, is it to be ascribed? 160° or not-a spectrum was scarcely made. That elasticity and consequent imperfect contact is not the sole cause of the incapacity of thin lamina of platinum and steel, for receiving spectral images, was to me rendered probable by observing that coins, placed on a thick copper plate, seldom were in perfectly close contact, yet gave good spectra. In order to come to a more definite conclusion on this point, I got a lamina of bright copper, even thinner, and as elastic as the platinum lamina above mentioned. Gold or silver coins left twenty-four hours on this, gave a spectrum scarcely visible; but on leaving a half-sovereign for two or three hours on it, exposed to a heat of 160°, as above, and pressed down by exactly the same weight, the half-sovereign left a permanent spectrum very well marked indeed. teen times. A sovereign left twenty-four hours or above, tarnished, gave scarcely a perceptible spectrum, and a sixpence none at all. On such a surface a sovereign was left on two different occasions, under a penny, for three hours, at a heat of 160°, and barely left a permanent spectrum of its outer margin; while on a well polished surface, at the same heat, the outline of the inpression also would have been left as a permanent spectrum in an hour or two. 11. Mass.-Mr. Hunt considers that mass Conclusions.-1stly, As brightness of the plate exercises an influence and increases the effect. is indispensable, and with brightness must exist In my experiments, however, I could not de- an increased tendency to tarnish, or enter into tect this. A farthing on a copper plate gave as chemical combination; 2ndly, as the plate must good a spectrum as a penny, and when heated be of an oxidable metal, and judging from the to 160° the farthing gave far the best, though experiments with silver and copper, the more the penny had a halfpenny laid on it. A four-oxidable the better; 3dly, as the more perfectpenny piece, too, gave as good a spectrum as a half-crown, pressed by another above it, in the same time, the contact being equally good in each case. The contact in these cases was made as equal as possible with the copper plate. 12. Does the thinness of the plate exert an influence?-A farthing (in two experiments) pressed by twelve or fourteen pounds weight, on a polished piece of platinum foil, in thirty hours left no spectrum at all; neither did it on a fourpenny-piece, or a sovereign, or half-sov ereign, when kept three or four hours at 160° under the same weight. I found a spectrum could be made on nearly equally thin zinc plates (zinc foil), by leaving a sixpence on it an hour or two. Zinc, not being elastic, allows the pressure to be equal. The particular chemical nature of platinum has, however, much to do with this effect; for I found that when a fourpenny-piece, or another small brass metal object was left on One spectrum, however, may be made on another; thus, after tale had remained eight hours on heated copper-plate, and left a permanent spectrum, a sovereign put on this an hour left a perma nent spectrum. ly the coins are cleaned and dried* the less the effect, and as a dry perspiration (so to call it) must exist in a greater or less degree on all coins, since they pass through so many hands, and as perspiration is slightly acid: 4thly, as even with clean coins the effect by actual contact must be admitted, but still is greater when there is a difference in the nature of the metal ; and 5thly, as when the metals are not in contact (being removed only the one-twentieth of an inch apart), no action or spectrum is evident, if the free circulation of air, and the connection * Moisture much increases the effect. Thus, when one surface of a shilling was rubbed over with ink, and such surface put on the copper plate and heated to 150°, a mark much more difficult to be effaced was left than when this degree of heat was applied without moisture. This is equally true, as will be remembered, with regard to glass plates. The general result of all the above experiments shows this; and of course an alteration of affinity from contact, is far more probable when metals are different than when the same; though if one be dirty, this makes it approach the nature of a different metal. catalytic action, meaning thereby an action so slightly chemical as, in the present state of the science, to be scarcely appreciable.* The attraction of glass and oxidable metallic plates for dust, &c., is very great; and is perhaps dependent on the same cause as their attraction for oxygen. Whether or not, I feel pretty well convinced, after a laborious investigation of the discovery in question, that it is not of that wonderful character that Möser and others have supposed; nor calculated to alter our ideas of vision or of the nature of light. On the contrary, I think with Fizeau (a short notice only of whose memoir I have seen) that no effect of any consequence is produced where organic matpolishing; for such is perhaps the philosopher's opinion just named, and in as far as our opinions agree, he has the priority. Begun by a purely catalytic action, it is only continued and developed in any marvellous degree when those circumstances are present that permit it to assume a more strictly chemical character. with dust be prevented-taking all these and minor considerations into account, we come to the conclusion that the effect in question is dependent on a chemico-mechanical action, or what Berzelius has called, catalytic action. No doubt it may be urged against this view, that the action takes place when the coins and plate are both heated, and hence quite dry. But this is no solid objection, for the adage, "Corpora non agunt nisi sint saluta," is not true, as hundreds of examples in chemistry show. The very fact of heat itself increasing the effect is all in favor of a chemico-mechanical view; for heat increases the tendency of copper to oxygenation, and tends also to volatilize any feeble acid matter on the coins. But again, if it be said the spec-ters are carefully removed by boiling water and trum rubs off, even when permanent and clearly defined (as we have shown), and leaves polished surfaces under it,-this we admit; but still this surface has suffered an almost imperceptible degree of oxygenation; for so slowly does this effect take place, that it is only visible when much advanced, as will be evident to any person who watches the gradual tarnishing of copper plates. Möser's discovery shows that very slight chemmical action is often going on, which has been previously overlooked. PUNCH'S OSSIAN. DUAN 1. MORNING rose on St. Giles's. The sun, struggling through mist, tinged the summits of the Seven Dials with the yellow hue of autumn. Gloom Sleepless was the wife of M'Finn. hung on her brow. Gone was M'Finn, of the light heart. To join his countrymen was he gone. Sacred was the day to Patrick. The chief difficulty that occurs to the above view is, that the effect takes place, to a slight extent, on glass; but in all my numerous experiments I have found that the effect is much less on glass than on well polished copper; for in no case has a permanent spectrum been made on glass, even by the longest contact.* It will also be remembered, that I found no effect whatever produced on talc. Now the tale scratches easily, glass of course does not; but talc is probably less soluble in acids than glass; at least in my trials it did not seem at all acted Why did gloom darken the brow of the wife on either by nitric, muriatic, or sulphuric. To of his bosom? Supreme in her heart he reignbe sure, you perceive no effect of these on glass, ed. Great was her love. Why burst the sigh but it does not seem impossible but that some from her lips?very slight effect takes place, and that the alkali is very feebly acted on, as glass is a compound body. By her not unseen was his danger.-Bereft Contact, at all events, may be presumed to have was the wall of his blackthorn. His tongue was an influence on the affinities of one of its ele-swift, careless his heart, and his arm strong. ments, whether there be even the slightest de- Neither was his soul patient of wrong. gree of decomposition or not. Now this influ- -A vision wraps her. On her spirit gathers ence is the catalytic influence; for it has been darkness. She foresees evil.-Is it M'Finn shown above, that without actual contact, and they bear lifeless to his habitation?-Her breast when all dust is kept off, neither silver nor cop-heaves sighs. Her hair streams loose on the per, even at the one-twentieth of an inch from winds She shrieks! She swoons! the glass plate, produce any effect, though kept there ninety-six hours. (See section 4, of heat generally, end). In consequence of this slight alteration in affinity, the parts of glass which have been in contact some time with coins or other substances, condense the breath differently from those parts which have not: hence the spectrum. The effect of glass, supposing it not susceptible of a gradual change by the action of air similar to oxidation, is rather in favor of the spectrum depending on a mechanical than a chemical action. I have in consequence ascribed the effect to a mechanico-chemical action, or a Hearken. * * ** * * * Pledged was M'Finn to Matthias to drink the purling stream.-Loud was the laughter of his friends. Broken was his pledge.-Thrice was the cup filled to the brim. Thrice raised to his lips. Thrice was it returned empty. His spirits rose. Loudly rang his laughter through the Hall. * In coming to this conclusion I have not forgotten another difficulty, viz., why a well polished and boiled copper coin produces a spectrum on copper plate. The effect, even when continued an hour or two at a heat of 160°, is very slight, and I found it to disappear entirely by twice breathing on the plate. Contact, then, of the same metal SLIGHTLY modifies chemical properties; such on the present view is the inference to be drawn from this fact. 1843.] ANNUAL RHENISH MUSICAL FESTIVAL. THE WORDS OF FAITH, ETC. His lips were opened: "Sons of Erin," listen to the words of M'Finn. His soul is great within him. It swells. Unable is his body to contain it.-Where are his friends?-Hath he not one among all his brothers to repress his swelling spirit? Is he alone, that they heed him not? And despised, that they do not regard him? M'Finn throws down his hat on the earth, cold as marble; is there no one to kick it? His coat, and will no one tread on it?—Is glory departed from Erin? Are her sons cowards ?. -Speaking, his rolling orbs flashed fire. Sore was his spirit moved. --Arose O'Flaherty of the auburn locks. emerald !-Are we cowards ?-Shall the cur -He spoke. And the gathering storm broke forth in thunder. Lightning flashed from opposing eyes.--Grasped was the shillelah, and the threatening arm extended.-In equal bands the sons of Erin form around their chiefs. Their souls are kindled.-The hall resounds with fearful crash of arms.-Like the hillstreams, roaring down,-the fierce blows of M'Finn descends.--Frequent as hail-stones are the blows he wards.-Stout is his heart; despising danger.-The walls, re-echoing groans, are sprinkled with the blood of the brave.-Hot is the fury of the battle! Fast fall the mighty. One by one they fall. Overpowered, the friends of M'Finn retreat, heedless of the voice of their leader.-Turning to rally them, a treacherous blow brings him to the earth. THE WORDS OF FAITH. From the Dublin University Magazine. FROM SCHILLER. "Drei Worte nenn' ich euch inhaltschwer." 411 Vailed in three words a solemn meaning lies, Yet not from outward things do they arise, Man would of every virtue be bereaved, Man is created free, and he is free, Though born in chains where stern oppression Fear the rude slave who rends his bonds in But fear not him who never felt the chain. And virtue lives-it is no empty name; Hid from the wise-its power unseen, un- It dwells in child-like hearts, and in those hearts alone! There is a God! there lives a holy will, Guard well these words!-in them deep meaning Let men from lip to lip those words impart ; Man of his virtues ne'er can be bereaved, ANNUAL RHENISH MUSICAL FESTIVAL.-The great annual Rhenish Musical Festival is to be held this year at Aix-la-Chapelle, on the 4th and 5th of next month. Upwards of fifteen hundred performers will be assembled on the occasion. The programCARICATURES.-There is a new artist and hume will include, First day, a Magnificat by Du-morist in the field, or we are mistaken. Here we rant; Mozart's symphony in G minor, and Han- have an etching, by "Pam," of Sir Robert as an del's oratorio of "Samson." Second day-the Income Tax collector presenting his demand to "Sinfonia Eroica" of Beethoven; an unpublished the keeper of a china shop, who significantly, but psalm, by M. Reisseger (under whose direction the with savage resolution not to be shaken, bids him performances will take place); a hymn by Cheru-"Take it out in China." The very crockery seems bini; another by Volger; and the overture to "Les Francs Juges," by M. Berlioz. This eccentric composer, by the way, is exciting a sensation in the Prussian capital. A second concert at which some of his works have been performed, seeming to have been more successful than his first. Our next news from Berlin will probably tell us of the first performance of the "Medea" of Euripides, with Mendelssohn Bartholdy's choruses. -Athenæum. to threaten, and a brace of brandy-flasks in the form of pistols are ominous of the issue. The state of trade and circumstances are cleverly intimated by the accessories-the spiders have woven their webs in places which good ale should have moist. ened-the ugly "mugs" grin at the collector-a little Staffordshire poodle has turned his back on a Staffordshire Wellington, and looks unutterable things-even a China jar has a history on the face of it.-Athenæum. |