PROFESSOR BICKERTON'S LECTURES.

Star (Christchurch), Issue 2037, 17 September 1874, Page 2

PROFESSOR BICKERTON'S LECTURES.

The fifth pf Profeasor B.ibkerfcph'sleetiwe'Bi ■'", on " Matter and Energy," was delivered afc .t^e Oddfellows' Hall on Thuraday evening .fo- a densely crowded, audience, the hall being filled sometime before the commencement of the lecture;::- ;-,- ■; kk''k ! ' 70 ■'• k'k f; . ■■•. Profeaßpr.-Bickeffoh, who was loudly* Applauded, aaid— Ladiea and gentlemen, mylha% lecture treated of the energy of ! the sun, the enormous amount of that energy whiohifaUs upon' the earth, and how that great loss of energy might be, made: good. I mentioned that all kinds of work/oxeoufced on the earth were executed at. thei expense of the' sun's energy, with one exception,' namely, the. tides. I also spoke a little on . the ..- manner in Which voltaic , electricity was produced,., and I showed that it also waa one pf the many forms of energy into which the sun's heat was conducted. Thia evening will be devotedJto the converaion of voltaic electricity into other forms of energy; You saw, amongst the ex**, perimenfca in my aecond lecture, that , ;wheuX rubbed a piece of glaaa with silk'ah atfcractile 1 force was developed on 'the glass, which is, called positive electricity, so when BeaUrig'-wa"x* was rubbed wifch flannel a similar force, which, is called negative electricity, waa developed," Last week, I told you respecting the .metals, and remarked on their various powers- x>f oxidation. . We saw that; some combined moat readily with. oxygen, and some, burnt even in the ordinary air ; " especially, wo noticed that? ' this was the. case with zinc, which metal forms' : the basis of most kinds of voltaic batteriesi: and its power of oxidation is the origin of their energy. Whenever we place in an acid solution . a piece of zinc and a piece of another metal having leas affinity for oxygen, ; eaohb^conjeßk charg< d wifch a weak charge of pppOßifce^ kinds!/ • : of electricity. When the two pieces of metal 7 are connected by a conductor of elecfcricifcy/the ' ■':. two kinds of electricity rush together. ******he zinc them' commences to dissolve in the acid*k and the energy of thia chemical action, in '-,; aome way causes the metals to become in- . stantly recharged with electricity; As thei ' are connected by a conductor fche two > electricities again combine, and* aa . thia proceaa ia continuous, a current of elec- .. ' ; , tricity pasaes along the conduofcor until some / of the materials are' exhausted. This con- - tinuous combination of fche two electricities ~mfche conductor is called voltaic ', elecfcrioifcy, and aa there ia a kind of flowing together in fche generation of this kind of electricity this ' action is termed the " voltaic current," and asthe action takea place within the acid, as well > aa in the conducting wire, fche whole, system of action is termed tho voltaic circuit. Thus much for the production of the voltaic ouivi* ' rent. We will now go on to speak of theconveraion of this current into other forms of energy. Voltaic electricity haa its origin in chemical combination, and ifc possesses fche power of taking fco pieces chemical substances. I hold in my hand two wires, each being connected with the opposite poleß of a battery charged in the manner I have previously v stated. Before me ia a vessel of acidulated ' water, in which two plates of platinum are inj»"* mersed; over each plate ia placed a tube of gla&B k alao filled with water. On connecting the plates ' with the battery by means of the wires, they '' ' become charged with oppoaite electricities. ' The hydrogen of the water, which ia a positive. - element, ia attracted by the negative platinum * , pole, whilst the negative oxygen ia attracted 7 by the positive platinum pole. Thia attraction ia ao powerful as to separate the atoms from... : one another, and thus fche water is split up into ita elements. The gaaes aro now being " evolved and are displacing the water from- the . t upper parte of fche tubes. "When a sufficient * quantity of water haa been decomposed, we ' shall be enabled to - exhibit the properties of its constituent elements. The oxygen, as usual, will cause a glowing splinter to burst ; into a flame, and the hydrogen will burn. I ; will now place a cell containing acidulated : .water into which dip two platinum wires in. ' the oxy-bydrogen microscope. You now see ; the two wires oa the screen* On connepting

them with the batfcery, bubbles of gaa are instantly liberated, and look, on the screen, as though a number of cannon balls were being created from the wire. (Laughter.) In addition to water, the voltaic current will decompose metallic solutions. I have here two plates of platinum connected with a battery. I plunge theae platea into a saturated solution of sulphate of copper. I now remove the plates from the solution, and you will see that the energy of the volfcaio current has effected a chemical decomposition, and deposited copper ih a metallic form on one of the platinum plates. (Applause.) Ifc is the smaller plate* that has thus been coated ,- the larger one remains perfectly clear. Ino remove the plates and place the small one on fche wire to which the large one was formerly a'fcached, the .large one occupying the wire lately connected with the small one. I again make contact with fche battery, and now the . copper haa disappeared from the small plate, whilst the large one is coated with it. (Loud applause.) Here, then, we have an illuafcra- " tion of the power of the voltaic current to effect the decomposition of metallic solutions, and now I will describe the manner in which ; this can be applied to useful purposes. If I attach to each of the poles of a battery a piece .of . metal, such as silver or copper, and dip them into a solution of a salt of the same metal the voltaic circuit will be completed, "and the solution will be decomposed into ita original elements ; the liberated metal will be deposited on one of the plates, whilst the acid thus set free will dissolve the other "plate, and thus the strength of the solution .will be kept up. If, therefore,! were to place a metallic tea-pot in a bath containing a solution of salt of silver, and connect ifc with one- pole of a voltaic batfcery, whilst on the other pole I hang a piece of silver in the solution ; on completing fche circuit;, electrochemical action will commence, and deposit the liberated silver on fco fche tea-pot, whilst at the same time the silver at the other pole .of the batfcery will be dissolved. Here, then, you have an illustration of electro plating that has placed objects bf beauty within the reach of almost every one. By this process, alao, it is possible to copy an engraved copper plate, so .that the number of pictures which may be obtained from these copies is almost without limits. It is in this manner thafc such an enormous number of the Ordnance maps of England are produced afc tbe Survey Office in Southampton. By fche aid of electrofcyping .'and eleotro-plafcing many beautiful works of art may. be reproduced. That exquisite speoimen of artistic skill, the Milton shield, which was exhibited by Messrs Elkington and Co., and whioh cosfc many hundred pounds, has been faithfully reproduced in copper, and these copies are sold as low as £7 or £8, thus placing ifc within fche reach of many who otherwise would nofc be able fco ornament; their dwellings with this fine work of art. I will now try a few experiments illustrative of the magnetic effects of the voltaic current. I have here' a magnetio bar, accurately balanced on a point, so fchafc ifc may revolve freely. The magnet now points north and south. Immediately abpve and parallel to it is stretched a thiok copper wire, I now send through thia wire a current of eleotricity ; to the eye the wire is unchanged, bufc not ao to fche magnet; wbioh you see has turned from its original direction, and now stands across the wire. Oa suspending the magnet above the wire it turns in the opposite direction. It also turns in the oppoaite direction if fche current be reversed. These phenomena constitute CErsted's great discovery — a discovery which, to the unenlightened, might appear comparatively useless, but wbioh, nevertheless, haf^been fche means of bringing about results of the greatest value to mankind, for upon the connection between voltaic electricity and magnetism is based the construction of the electric telegraph and an almost infinite variety of other useful appliances. The apparatus I have juafc shown can be rendered muoh more sensitive by coiling the wire several times above and between the length of the magnet; the system then forma what; is called a galvanometer, and the magnet will move under very feeble currents of electricity. I have here auch an arrangement, and you ace With what; energy tbe magnet; moves backwards and forwards each time I reverse fche current. (Applause.) This ia fche principle of -Wheatstone's telegraph, only tbafc the magnetic needle and coil, instead of being horizontal, are placed vertically. In yonder window you will ace a large model of Wheatstone's telegraph. On sending the current through these wirea, which are connected with the telegraph, the needle ia deflected to one side, the current being reversed, the deflection takeß place in the opposite direotion. Suppose one movement to the right to represent the letter T, one to the left the next most frequent letter ; thus, by a series of movements from left to right, or from right to left, the whole of the letters of fche alphabet may be represented. We have seen the effect fche eleotric current haa upon the magnet. I will now proceed to develope still further the effects of this current, bo aa to produce temporary magpets of the moat powerful character. I take an iron rod and plunge ifc amongst a number of nails; they are nofc attracted, because the bar possesses no magnetic force ; but I now coil around the iron bar aome copper wire insulated by being covered wifch cotton thread, and connect; fche enda of thia coil with a voltaic battery/ the moment contact ia completed the current flows through the coil, and the bar becomes a magnet and attracts the nails readily; but when the contact is broken, the magnetio power ceases to exist in the iron bar, ahd fche nails drop off. (Applause.) In performing fchese experiments, we must uae a bar of soft iron ; if a bar of steel were uaed ifc would become a permanent magnet. The most powerful form of electromagnets is the horse shoe. I have here a small horao shoe of soft iron, around which ia coiled a copper wire covered with cotton thread. Ifc haa now no magnetio power, and has no attraction for iron ; bufc fche instant I connect it with tbe volfcaio battery, ifc becomes a powerful magnet, . easily supporting this iron ot half a hundred weight. (Applause.) I break contact with the battery, the magnetic force, ceases, . and the half-hundred weight falls fco the ground. (Renewed applause.) Bufc this exhibition of electro-magnetic energy is comparatively feeble in its character. Here is an electro-magnet of much larger dimensions. I apply to the polea a bar of iron. You ace there is nofc fche slightest attractive force. I new make contact with the battery, and the horse shoe haa become a magnet possessed. of the greatest energy. Look, with all my efforts I cannot detach the iron bar from the magnet; ; I can bend ifc, bufc so great; is the attractive force thafc fche bar will nofc come off . (Applause) I break contact, and the bar rolls off into my hand. (Renewed applause.) I again make contact with the battery, and the iron bar is not only firmly held, but has also become a magnet; possessing all the power of attraction, co that I am enabled ta attach to it a small pyramid formed

SMM^MCPCSTS^^-Hl. *."!Jl3**«»gJg,. II .■■^.U. / *MUUI J IJjl L,,S I JS^»gSSWPSgfPg*^B^BBSS of • other iron bars. I break the electric circuit, and fche p, ramid falls fco fche ground. (Applause.) Here is another interesting experiment. In a wooden tray, wliich is supported on the poles of the iron horao shoe, I place a number of nails. So long as the horse shoe is unconnected with the battery, the nails Ho perfectly still, thero being not fche slightest attraction ; but no sooner do T complete the electric circuit, than each nail seems inabiuob with life, und the whole bristle up like tho spinoa on a hedgehog's back. By a little manipulation, lain enabled to form with the nails, a rustic arch of considerable height, fche nails being held in poaition by the mag? nefcie force developed in fchem. I break contact, and ace, our symmetrical arch falls into a mass of ruin. (Loud applause.) You can easily imagine tbat an arrangement; may be made for .driving' machinery by a force developed in this manner, although the great expense of obtaining the necessary battery power will prevent ifc being adopted until coal becomes far scarcer. Here is a little engine moved by elecfcro-magnefcio power, working very energetically at a pump which is sending oufc a continuous stream of water. This scientific toy is constructed as follows: — A brass wheel has pieces of aoffc iron rivetted on ita circumference at equal distances from each other ; a small electro magnet; ia placed underneath the wheel, and aa the current passes, the magnetism being developed, attracts one of the piecea of aoft iron. By a mechanical arrangement the contact is broken as soon as the pieoe of soft iron reaches the magnet ; the wheel, by its own inertia, continues to move on, and in doing thia makes contact and establishes fche current once more • the next piece of aoffc iron is then attracted, and thia continues along the circumference, keeping tke wheel in motion until I remove the connecting will from the model. I have here another form of engine working on the aame principle of electro-magnetic attraction, but in this caae the magnet rotates, whilafc fche soft iron stands still. With the exception ef a mathematical instrument maker's workshop in Paris, I am not aware that this haa been turned to practical use. Affixed to the front of yonder gallery is a little piece of mechaniam, very commonly used in hotels. I mean the electric bell. It is worked by a small electromagnet, having an automatic contact breaker, so fchafc fche current alternately passes and ceases, and thus the bell is rung; a continuous ringing may be kept up so long as tlie instrument is in connection with fche battery. I now complete the circuit, and the bell commences to ring, I disconnect fche wire, and it afc once ceases. (Applause.) The force of electro-magnetism ib utilised in many waya. Morae's printing telegraph being an example. Here ia a model, on an enlarged scale, of this telegraphic instrument. In Morse's telegraph a continuous atrip of paper is made to pass, by means of clockwork, regularly over a small drum. If a pencil, or any other instrument capable of making a mark, be made to press against the moving paper, obviously a line would be drawn on it; here is such an arrangement. In thia case, I have used a small brush containing ink, it is, attached to one end of a lever, fco the other end is fixed a piece of aoffc iron, placed immediately above the poles of an eleofcro-magnefc. When fche current; passes, the aoffc iron ia attracted downward, and the brush at the oppoaite end is lifted up into contact with the moving paper, and a line is made which is the case every time the current passes through the magnet. If the passage of the current were simply instantaneous, a dot on the paper would be the result, and thus by Bending the current for a greater or lesßer period, dashes or dots would be made. By a little combination fchese are made to represent the letters of the alphabet. My assistant will make contact with a distant battery, and you see by this piece of paper, which I now tear off, thafc dots and daahes have been made. (Applause.) Here then in these experiments of the magnetio effects of fche volfcaio current, we see how the chemical energy of the batfcery ia converted into electricity, fche electricity infcd magnetism, and the magnetism into mechanical work. The voltaic current alao produces physiological effects which moat; of you doubtless have frit from the email medical coila now ao common. The coil I have here, would be sufficient to give a shock to five hundred people at once. We will now go on to consider the conversion of electricity into another form of energy, namely, heat. I have here two upright; rode, one of metal and one of wood, stretched - from rod fco rod are several wires of different; metals. The metallic upright is conneoted with one of the poles of a powerful voltaio battery, 1 hold in my hand a copper wire, conneoted with the other pole. On bringing this wire into contact with any of tbe wires near the wooden upright, ifc ia obvious that a current will be senfc through them. On thus placing: it in contact with the copper wire no result ia obaerved ; but, on making contact with the platinum wire, its whole length becomes white hot, and glows brilliantly from the intensity of the heat developed. The eleotricity flows freely-through the copper wire ; bufc, in fche platinum, the current passes with difficulty, and, owing to the resistance which ifc experiences ih its passage, the energy of the eleotricity gives motion to the molecules and heat is produced. On a former occasion, when epeaking of heat, I showed you what a wonderful difference there was in the power of different substances tp allow heat fco pass through fchem. We saw with what rapidity the heat travelled through fche length of a piece of copper and ignited fche phosphorus placed upon ifc, whilst in the mineral asbestos we had a substance in which heat flowed so slowly, that by placing a thin layer of it on my hand, I waa enabled to hold a red hot iron ball for a considerable time. So with the electric current ; in some substances it flows freely, and theae we call good conductors, in othera it passes only with extreme difficulty, and they are, therefore, called bad conductors. The metals are all good conductors, bufc differ considerably as fco fcheir powers of conduction. When we wish to develop heat in any particular place, we uae good conductors up to that spot, and thero we put a worae conductor, that through fche resistance fche current meets, witb, ifc may be converted into heat. Across the hall, I have hung a festoon of alternate lengths of copper and platinum, one end of the festoon is connected wifch the battery, and the wire I hold in my hand ia attached to fche opposite end. The festoon at preaenfc is quite invisible to me, and ia probably ao to all of you, but; immediately I make contact with the batfcery, and send the current through the festoon, every piece of platinum glows like a star, appearing aa if auapended in air. (Applause.) This experiment forcibly illustrates the different conducting pewer of platinum and copper wire, for the same current which had made the platinum white hot, has not in the slightest degree heated fche copper wire which I hold in my hand. On Bending the eleotric current through two copper wirea stretched across the room, tbe ends of whioh are joined by * piece of platinum wire,

sufficient Wat aay ■.«. de*- -'.oawl toigniu* ii' piece of gun cotto» plne-i? ground <"be platinum *ir** I sen..' fch« •nrivnt und ihe gun cofctci. bi-j-ua ". i ■;"yb;i?: ; >i' , fc fli?'*i (Applane- } Tl ;fi -j .-n •''■'<•[■'■■-. '■" 'bet- i ;•■•«. principle o > !.<. ippli 'jj :: ;■ . in a. cr fiblaating p.-v^ives. f -'^v*- •■■ tb> « ; ay propared a str.aii torped-..* ■*. p: . -ed it on tho N>*> of yonder cu-niue, i i-* vi ■.■•■iy a litlle <?un cotton rolh-<.! <iy ta }•• . ■ >i I send tiie current tir, »ugh tbf* ..it*. ani 7 *jas • » exploded v-i'li v lo * •.<! .* ii- ud ;•*■• plause.) B?,.j\. h-.u .-. ; ... ..*'.•? i-ffe ■ r-: of electricity I ehouid like :i> aay a few words respecting an instrument I have here, called an induction coil which, ia- frequently uaed where ignition ia required in several places at the aame inatant; The kind of electricity wehave hithetobeen uaing this evening may be likened to an immense river, which haa to flow down a short incline, whilafc the electricity of this induction coil may be likened fco a small stream of water falling from a vaafc h eight i The coil plays the part for electricity that the hydraulic ram doea for water. The hydraulio ram uses up a short fall of a large quantity of water, wastes mosfc of it, but will send a little to an enormous heigth. So fche induction coil uses, up a large quantity of electricity' of low power, but; gives forth a little of high intensity. The current fchafc enters this coil ia almoafc incapable of leaping an interval at ail, whilst fche electricity that leaves it is capable of darting across an interval of several inches. I how send through the current, and a torrent of brilliant sparks passes between the two poles. On that windowsill is a row of nine gas-burners," along the length of which runs a wire ; afc each burner; the wire is cut, and a short interval is left between fche ends. On joining the two ends of the wire with our coil, and sending the current through, a continuous flow of sparks may be observed passing above eaoh burner, and on turning on the gaa, each burner is instantly ignited. (Applause.) So much for the heating effects of the current. We will now treat of ita luminous effects. Whenever any solid body is intensely heated it becomes luminous, as we saw in the caao of tbe platinum wire, but the most beautiful illustration of the luminoua properties of the electric current is when it is allowed to pass through glass tubes containing highly rariued gases. ' Suoh a tube ia before you. Could anything be more exquisitely beautiful than fche luminoua effect; produced in fche tube by fche passing current. (Applause.) The light appears to be continuous, but in reality ifc consisfca of a series of flashes. This, I think, I can make evident to you. Some similar tubes are attached to this disc, which ia conatruoted bo aa 'fco revolve rapidly. The tubes are now luminous wifch the passing current, apparently glowing with a steady light ; the disc is now made to revolve, and instead of obtaining circles of light as would be produced by fche revolution of an ignited stick, a star, composed of a series of distinct images of the luminous tube, appeara. (Loud applause.) Thia most; beautiful experiment demonstrate* in a striking manner fche discontinuity of the light. Tho most powerful illustration pf the light produced by voltaic eleefcrioifcy ia developed when fche current; passes between two pieces of hard carbon. Carbon being capable of enduring an excessively high temperature without volatilization, can be heated so as to produce a light of dazzling brilliancy. I have here a lamp for producing this light., and on passing fche current from Grove's batfcery of fif fcy cells, the light is so great that the gas and candles, instead of illuminating, actually cast; shadows on the walls and ceiling. ' The light itself is so brilliant; fchafc we cannot; look afc. it and see what it is like/ but by placing the lamp in thia . lantern, an image of the two carbon points is seen upon fche wall. You see that they are separated by a distinct interval, and I hope, in aome f uture lecture, to prove thafc this interval is due to a connection current of air carrying the electricity from one pole fco the other. .We have thus this evening traced the many forms of energy into which voltaio electricity j maybe converted, and in the next lecture I ■ hope fco show you somewhat; of the properties j of the radienfc energy of the lights which is passing off in every direction from this eleotric light. (Loud and prolonged applause). The experiments, which were of a very brilliant character, were mosfc successfully carried out, and the Professor waa listened fco with great attention throughout;. The concluding lecture of fche series will be given on Thursday next.