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Dr. Cora Angier Sowa

CORA SOWA'S RIGHT-OF-WAY:

RAILROAD (AND ENGINEERING) HISTORY OF CORA ANGIER SOWA

Excerpts from Hippolyte Fontaine, Electric lighting: A practical treatise 1877, translated from the French in 1878 by Dr. Paget Higgs

To be read in connection with

Engineers in the Family, Part III

Russian and American Life of Alexander Lodyguine, Russian Inventor and Engineer


Click here to go back to "Life of Alexander Lodyguine"

Who invented the electric light?

An introduction to the quoted excerpts:

The question of who invented the electric light continues to interest historians. The debate was intensified during the Cold War, when the U.S. and the Soviet Union issued duelling postage stamps honoring, respectively, the American Thomas Edison and the Russian Alexander Lodyguine as inventors of the incandescent light bulb. Actually, the matter is, as expected, much more complicated than that, with scientists and inventors from England, Germany, France, Russia, and the United States, over the course of many decades, trying many different solutions to the problems the project entailed. (Today, of course, the quest continues, as new kinds of lighting, such as light-emitting diodes (LED), are experimented with.) An entire page of this Web site is devoted to the life and career of Alexander Lodyguine, who was married to my mother's Aunt Alma.

To provide detailed accounts of the many inventions (and some of the patent disputes!) comprising the history of electric lighting, I include as Appendices passages from two early writings (of which full texts are available on Google Books):

  • THE PRESENT PAGE: Excerpts from Hippolyte Fontaine, Electric Lighting, 1877. (For the complete text on Google Books, click here.)

  • Edwin Hammer, "Incandescent Lamp Development to the Year 1880" in Electrical World and Engineer, December 1, 1900. (For the complete text on Google Books, click here.)

For a short modern summary, see William Hausman, Peter Hertner, Mira Wilkins, Global Electrification: Multinational Enterprise and International Finance in the History of Light and Power, 1878-2007 (Cambridge Studies in the Emergence of Global Enterprise), Cambridge University Press, 2008 (paperback 2011), p.11. In this account, credit for the first commercially viable incandescent light should perhaps be given to the Englishman Joseph Swan. (For the text on Google Books, click here.)

Contact Minerva Systems To return to the Minerva Systems home page, click here.
To return to Page 8 of Cora Sowa's Right-of-Way, "Engineers in the Family III (Alexander Lodyguine)," click here.
To return to the first page of Cora Sowa's Right-of-Way, click here.

You can also contact me at casowa@aol.com.


Hippolyte Fontaine, Electric lighting: A practical treatise, 1877, translated from the French in 1878 by Dr. Paget Higgs and published in London (quoted in Electrical World and Engineer, December 1, 1900)

The following excerpts are those of particular relevance to the work of the inventor Alexander Lodyguine (Lodyguine's name has been emphasized in these excerpts in boldface for easier reference, beginning on page 171). To read the complete original text on Google Books, click here.


CHAPTER XI.

LIGHTING BY INCANDESCENCE.

p. 168

Use of Geissler Tubes - Report presented to the Academy of Sciences by M. Coste, in the name of M. Gervais - King's Invention - Lodyguine's Lamp - Wild's Report to the St. Petersburg Academy - Konn's Lamp - Bouliguine's Lamp - Experiments by the Author on Lighting by Incandescence - Cheremeteff and Fontaine's Lamp.

As we have said, the voltaic arc is eminently convenient for the lighting of large uncovered spaces, or large halls without interior partitions, but when it is required to light small places or very subdivided localities, it is much more advantageous to employ gas, petroleum, or even ordinary oiL

There are numerous works on the construction of small electric foci, but to the present day none of the means devised have given practical results. It has been endeavoured to use Geissler tubes, and small incandescent carbons, and if these two means have not been successful, they offer nevertheless sufficient interest that we should devote some pages to their description.

It is well known that Geissler, an artist at Bonn, constructed the first tubes blown in various forms, closed hermetically and containing only traces of various vapours. These tubes put into communication with a current, by means of platinum wires fused into the glass, from a Ruhmkorff coil, produce a stratified light, that is to say, composed of fine transverse layers separated by dark layers continually agitated. At the same time the sides of the tubes present a brilliant appearance, to which the term fluorescence has been applied.

On March 27, 1865, M. Coste presented to the Academy of Sciences, in the name of M. Gervais, the following report:

"The apparatus was constructed by M. Ruhmkorff, who has acquitted himself of his task with his usual care and ability. It is a case or box in bronze, mounted on four feet, and its cover

p. 169

or lid is hermetically closed by means of a press-screw, and between the two surfaces thus brought into contact is a caoutchouc washer. To the cover is attached a ring, serving as a suspension to the optical apparatus. The case contains two bichromate of potash elements closed in their turn by plates to which strips of copper are solidly screwed. The poles of the current furnished by these two elements may be put at will into communication with the bobbin, and the induced current is transmitted to a Geissler tube by two wires covered with india-rubber. This tube, of proper form and filled with carbonic acid, is enclosed in a glass cylinder with thick sides, furnished with copper armatures, and into which water cannot penetrate. This is the lighting part of the apparatus. With this instrument a soft light is obtained, similar to that now employed by miners. It resembles in certain respects that given by phosphorescent animals, but is more intense. It can be seen even when the apparatus is several metres under water. It would doubtless serve to attract fish, as does the phosphorescence of certain species, and it would also serve to light limited spaces, situated beneath the surface of the water, or for floating signals. The captain of the 'Devoulx,' commanding the southern coasts of France, employed this apparatus in the port of Cette, in September last. It remained immersed for nine hours, and it gave light for six hours under these conditions, as well as when charged at Montpellier. The phosphorescence may be of longer duration. A second trial, made at Port Vendres, on board the 'Favori' (Captain Trotabas), was equally successful."

The light obtained by the Geissler tube is so feeble, that it can never be utilised practically, and numerous trials made in mines and powder mills have been without result.

Lighting by incandescence has been studied for a long time; but its application generally presents so great difficulties, that at the present day it may be considered as within a purely scientific domain, although a certain number of apparatus exist working moderately welL

The first document on the question that we have found, is an English patent of the 4th November, 1845.

Mr. King, the inventor, enters into some exact details of his

p. 170

idea, and presents some considerations which tend to prove that magneto-electric machines, powerful enough to produce light, already existed in 1845.

The following are the principal passages from this patent: The invention has for its basis the use of metallic conductors, or of continuous carbons, heated to whiteness by the passage of an electric current The best metal for this purpose is platinum, the best carbon is retort carbon.

When carbon is employed, it is useful on account of its affinity for oxygen at high temperatures to cover it from air and moisture, as indicated in Fig. 45. The conductor C rests on a bath of mercury; the bar B is in porcelain, it serves to support the conductor C; the conductor D is fixed on the bell by a hermetically sealed joint. The carbon rod A rests at top and bottom on conducting blocks and becomes incandescent by the passage of an electric current.

King's lamp

A vacuum is previously established in the bell, and the apparatus veritably forms a barometer with one of the poles of the battery in communication with the column of mercury, and the other with the conductor D.

In order to obtain an intermittent light, the circuit can be periodically interrupted by a clockwork movement.

The apparatus properly closed may be applied to submarine lighting, as well as to the illumination of powder mills and of mines, especially where the danger of explosion is feared, or the rapid inflammation of very combustible substances.

When the current is of sufficient intensity, two or a larger number of lights may be placed in the same circuit, care being taken to regulate the power of the magneto-electric machines, or the elements of the battery producing the current.

In 1846, Greener and Staite filed a patent for a lamp, analogous to King's, pointing out that they freed the carbon,

p. 171

before use, from impurities by treatment with nitro-muriatic acid.

In 1849, Petrie concludes the description of a patent for a lamp with the following remark:—" A light may be produced by passing an electric current through a short and thin conductor, which heats and becomes luminous; but the majority of substances fuse and burn rapidly: however, I obtain a good light by using iridium, or one of its alloys. Iridium may be fused so as to produce an ingot whilst it is submitted to the heat of the voltaic arc; afterwards it may be decarbonised and rendered more malleable. It can be cut into small pieces of 0-001 mètre diameter and 0-010 to 0-020 mètre length, that can be fixed upon two insulated metallic supports, which are in connection with the two wires of a proper galvanic battery. There is then obtained a beautiful light."

Several other patents have been taken out in America, France, and England for the same kind of idea; but none of these appear more complete, more explicit, and more practicable than King's; it is then useless to continue our nomenclature.

Lighting by incandescence, and the principle of its production, had for a long time fallen into oblivion, when in 1873 a Russian physicist, M. Lodyguine, resuscitated both, and invented a new lamp, which has since been perfected by Messrs. Konn and Bouliguine.

In 1874, the St. Petersburg Academy of Sciences awarded a high prize to M. Lodyguine. The following includes some extracts from the report presented on the occasion by M. Wild, director of the Imperial Observatory; this report, as we shall see, includes several capital errors:

"It has long been known that we can employ the heating faculty of the electric current, even without the aid of gas, as in the luminous galvanic arc, to heat a solid body to whiteness. On this principle there are often thus heated thin platinum wires, which are bad conductors, by causing them to be traversed by a powerful electric current. The light obtained by this process is much more feeble and more constant than the electric light from carbon; it can also be extended further, and may be increased or diminished at will; nevertheless it has never found

p. 172

practical use, because it is too feeble compared with its cost, and because when it is desired to give greater intensity, there results fusion of the platinum wire, which in general is not homogeneous throughout.

"M. Lodyguine was the first who had the idea of replacing the platinum wire, in these combustion experiments, by small bars of carbon (coke) analogous to graphite, that is to say, a good conductor, and thus resolved the problem of electric lighting.

"The advantages of this substitution of the carbon for platinum are so obvious from a theoretical point of view, that it is astonishing, as is always the case with important inventions, that no one had the idea sooner. Carbon possesses at equal temperature much greater power of radiation than platinum; the capacity for heat of platinum is superior (nearly double) that of the carbon in question, so that the same quantity of caloric raises the temperature of a small bar of carbon to a degree nearly twice that attained by a platinum wire of the same volume. Besides the resistance of the carbon in question, as a conductor of electricity, is nearly 250 times greater than that of platinum; it results that the small rod of carbon may be fifteen times thicker than a platinum bar of the same length, and that the current traversing it will engender the same quantity of heat. Finally the carbon may by heated to the most extreme white heat without fear of fusion, as is the case with platinum. It is to these important theoretical advantages that is evidently due the great success of the mode of electric lighting proposed by M. Lodyguine.

"The sole inconvenience of the use of carbon instead of platinum consists in the fact that, in the combustion the carbon combines with the oxygen of the air, and is thus gradually consumed. M. Lodyguine has avoided this inconvenience by enclosing the carbon heated to whiteness by the electric current in a glass receiver hermetically sealed, and from the interior of which the oxygen is expelled by a most simple process.

"It is not within the province of the Academy of Sciences to give its judgment on the technical and other difficulties which will present themselves in the extended application of M. Lodyguine's invention, nor on the other hand, upon the

p. 173

numerous practical advantages of this mode of lighting above all others; it will suffice to the Academy to state that, thanks to this invention, there is resolved in the simplest possible manner the great problem of subdivision of the electric light, and of rendering it constant,*
[FOOTNOTE:] * We shall see subsequently how the problem has been resolved by M. Lodyguine.
in order to recognise M. Lodyguine as worthy, in consideration of the numerous applications of his invention, to obtain the Lomonossow prize."

In his lamp, M. Lodyguine employs carbon in a single piece by diminishing the section at the point of the luminous focus, and he places two carbons in the same apparatus with a small exterior commutator, in order to pass the current into the second carbon, when the first has been consumed. Nothing is less practical nor less studied than the apparatus of this inventor.

M. Kosloff, of St. Petersburg, who went to France in the hope of working the Lodyguine patent, perfected his lamp slightly, without, however, bordering upon anything passable.

In 1875, M. Konn, also from St. Petersburg, patented a more practicable lamp, represented in Fig. 46, which was constructed for the first time in Paris by M. Duboscq.

This lamp consists of a base A in copper, on which are fixed two terminals N for fastening the conductors, two bars C, D in copper, and a small valve K opening only from within outwards. A globe B, widened at its upper part, is retained on the base by means of a bronze collar L pressing on an india-rubber ring, exactly as occurs with the level-gauges of steam-boilers.

One of the vertical rods D is insulated electrically from the base, and communicates with a terminal also insulated. The other rod C is constructed in two parts: (1) of a tube fixed directly upon the base without insulation, and (2) of a copper rod split for a part of its length. This split gives elasticity, and admits of the rod sliding in the tube with only a small effort.

The retort carbons E, to the number of five, are placed between two small plates which crown the rods.

Each carbon is introduced into two small blocks, also of carbon, which receive the copper rods at their extremities. The rods also are equal in length at their lower ends, and of unequal length at their upper ends. A hammer I is hinged on the bar C,

p. 174

and rests only on a single rod of carbon at once. If this lamp is placed in circuit by attaching the two conductors from a battery to the terminals N, N' (the terminal or binding screw N' is hidden by the terminal N; but it is identical, and is not insulated from the base), the bar of carbon E is traversed by the current which passes by the aid of the hammer I, from the copper bar F, the two carbon blocks 0, 0, the copper bar Gr, and the plate crowning the bar D.

The vacuum has previously been made by putting the cock K in connection with an air-pump or other known pneumatic machine.

The rod E reddens, whitens, and becomes luminous. Its light is colourless, steady, and constant; but gradually the section diminishes, the rod breaks, and the light disappears. The hammer I then falls on another rod, and nearly instantaneously lighting is re-established.

When all the carbons are consumed the hammer rests upon the copper rod H, and the current is not interrupted. In this manner when several lamps are fed by the same electric generator, extinction of one does not cause that of the others.

To avoid the projection of small pieces of carbon and their blocks against the glass, M. Konn has placed at the lower part of his lamp a small copper tube M, which receives the débris until the plates are refurnished.

Three of these lamps were introduced two years ago at the house of M. Florent, a merchant of St. Petersburg, and put in action with an "Alliance" machine. Each carbon lasts about two hours, with the exception of the first, which is consumed nearly immediately; the light is very agreeable, but its cost considerably exceeds that of gas. M. Florent, whom we have had occasion several times to see, has informed us that the great advantage he has found in the employment of electric lighting was its cleanliness. His store-rooms contain much white linen that gas rapidly impairs, and on which electricity exercises no injurious influence. The bleaching economised fully compensates the supplementary cost necessitated by an important introduction, with but little regard to the light obtained.

M. Florent has not made any photometric measurement; but,

p. 175

Konn's lamp

p. 176

by comparison with gas, each Konn lamp has been valued at about 20 Carcel burners.

The principal cause of the great expense that the use of the light from incandescence entails, rests in the difficulty of preparing small carbons, which cost as fitted, more than 5 francs per mètre.

A Russian officer, M. Bouliguine, has constructed a lamp (Fig. 47), which attains nearly the same end as that by M. Konn with a single carbon. It consists, like the preceding, of a copper base or socket, two vertical bars, two bars carrying the curent, and an exhaust valve.

One of the bars is pierced with a small hole from top to bottom, and has nearly throughout its length a slot admitting the passage of two small lateral lugs.

The carbon is introduced into this bar like the lead of an ordinary pencil-case, and it is assisted to rise by a counterweight connected by two microscopic cables to lugs in the transverse support on which the carbon rests.

The part of the carbon which is to become incandescent is held between the lips of two conical blocks of retort carbon.

A screw placed on the base admits of increasing or diminishing the length of the bar which carries the upper conical block, and consequently of giving to the luminous part greater or less length.

The closing of the globe is effected by the lateral pressure of several india-rubber washers.

When the lamp is placed in circuit, the carbon rod reddens and illuminates until it is about to break. At this moment a small mechanism*

[FOOTNOTE:]* The mechanism in question, which the scale of the engraving will not admit of showing, consists substantially of an iron armature placed in the interior of the lamp, and of two metallic rods acting on two cross levers jointed on to the ring surrounding the carbon-holders.
commanded by an elecro-magnet opens the lips of the carbon-holders, the counterweight above drives out the fragments that would remain in the notch, and the counterweight below raises the carbon rod which penetrates the upper block, and re-establishes the current. The mechanism again acts, but in contrary direction to its first manœuvre, the carbon-holders contract, and the light is renewed.

p. 177

Bouliguine's lamp

p. 178

We have several times tried this lamp, but we have never obtained good results. It includes too many moving parts, and the least obstacle pervents the play of the mechanism. However, we have observed that when by chance it works regularly, the contacts being better and less numerous than those of Konn's lamp, it needs less intense currents for the production of a given light. With a Gramme machine of 100 burners we have obtained with a single lamp as much as 80 burners, whilst with a Konn lamp we could never exceed 60 burners. . .

-------------------------

p. 181

[On coupling together several lamps in a battery of lamps]

. . . We have recently made similar trials with Gaudoin artificial carbons of the same section, and the results have been more satisfactory. thus the total light produced with 48 elements in four series and a single lamp, reached 80 burners, and that produced with the same battery and three lamps, attained 30 burners.

The same battery coupled in tension and actuating a Serrin lamp gives a voltaic arc of 105 burners; but the light obtained by incandescence is much steadier and more agreeable to the eye.

From what precedes, it appears to result that King and Lodyguine's system is much more favourable to large foci than to the divisibility of the electric light; however it is proper to remark that when 10 burners per lamp are not exceeded, the carbons have a very long duration, whilst they are consumed very quickly for an intensity of 60 to 80 burners. . .

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p. 184

CHAPTER XII.

DIVISIBILITY OF THE ELECTRIC LIGHT

General Remarks on the Divisibility of the Electric Light - Impossibility of establishing very small Luminous Centres with the means actually known - De Changy's Invention - Report of M. Jobart - Lacassagne and Thiers' Dividing Regulator - M. le Roux' Experiments - M. de Mersanne's apparatus - M. Jablochkoff's Experiments at the Magasins du Louvre - A Recent Communication made by M. Denayrouse to the Academy of Sciences.

The remarkable effects of the voltaic arc were no sooner foreseen than the idea arose of dividing the electric light, and even before the existence of a good regulator for a single light, King took out a patent for a lamp on the divisible system. The steps, however, that were being taken to perfect the single luminous centre had advanced so rapidly, that with an expenditure of 10 horse-power an artificial sun of an intensity of 4000 burners was produced. This grand result was due to the carbons of Foucault, Carré, and Gaudoin; to Serrin's lamps, Gramme's machines, and Sautter and Magin's projectors. On the other hand the plan of dividing the light made no advance, but remained still an object of experimental and speculative inquiry.

The merits of the systems of King in 1845, and of Jablochkoff in 1877, are of an exceptional character, and it would be a matter of difficulty to decide which of them approaches nearest to the true solution of the difficult problem of dividing the electric light. It must not, however, be thought that in face of these obstacles the idea of replacing gas by electricity will have to be entirely renounced, for science is far from having attained the last of its conquests by means of this mysterious fluid, which has already annihilated distance, and may also be said to have suppressed night; but despite the remarkable labours of M. Jablochkoff, and the no less remark-

p. 185

able initiative of M. Denayrouse, there exists at the present time no sufficiently practical system of so dividing the light as to render it generally available for the purposes for which gas is used. Each decade gives birth to a new idea, the importance of which is exagerated by rumour until, after a few unsuccessful trials, public interest abates, and nothing more is heard of the matter, In 1847, King's discovery of incandescent carbons was announced in England; in 1857, M. de Changy, in Belgium, substituted platinum for the carbon, and employed a regulator; in 1867, M. Le Roux published in France a method of passing a current alternately, and with great rapidity, through several ordinary regulators; and lastly, M. Jablochkoff, in 1877, caused sparks to pass through plates of kaolin, and by this means obtained a series of small lights.

There is no doubt that each of the systems proposed is capable of rendering important service in special cases, but the error that inventors have fallen into has been the claiming of too great a scope for their apparatus as leading immediately to the supplanting of gas. The electric light has already a vast field of application open to it, and Chapters VII. and VIII. treat of the great advantages attaching to its employment in a number of cases, but that it will some day entirely take the place of gas is extremely improbable. It has, in fact, only been since the introduction of electric lighting that our admiration for the facility with which gas can be divided and distributed has been fairly aroused.

By the term "divisibility of the electric light" we do not mean the production of several intense lights by means of one machine or battery, but simply the maintaining of a few small luminous centres, each equal to 1 to 15 Carcel burners. It has been proved beyond a doubt that several lamps can be kept in action by one magneto-electric machine, but the question is, whether the first cost and maintenance of such apparatus is not greater than that of a series of small machines each in circuit with a lamp. We have always favoured the latter method of lighting, although the other plan has received a large share of our attention, and there is a likelihood that M. Gramme will still have the honour of making it a practical success. At

p. 186

present, however, the means proposed for attaining this divisibility of the light have been practially without success.

We will now glance at the various systems devided for the solving of this problem. It has been shown that the invention of King, re-invented by M. Lodyguine, and improved by M. Konn, was better suited to a single light than to a divisible system. There are, however, some advantages connected with the burning of small carbons in a vacuum, inasmuch as the light is steady and the expense moderate. Before abandoning this method some new experiments should be made with shorter and thinner carbons of various qualities. Where a single lamp and great regularity of the light is needed, this system may come into use. The mode of operation adopted by M. de Changy has never been thoroughly known, but to judge from the following communication made by M. Jobart to the Academy of Sciences on the 27th of February, 1858, M. de Changy's laboratory experiments must have been perfect: . . .

-------------------------

p. 190

. . . Last year, when travelling through the principal towns of the United Sates, we endeavoured to discover what progress had been made in America, in the matter of electric lighting, but we were unable the see anything of a practical nature. Many phsyicists had been experimenting with a view to the division of the light, but none of them were in a position to show us an apparatus worthy of even being mentioned. We wil only refer here to a patent taken out by Mr. Henry Woddward, in 1876.

This invention relates to the incandescence of a carbon in a

p. 191

rarefied gas, having the property of not combining chemically with carbon heated to redness.

We have already mentioned the arrangement of parallel carbons forming the candles of M. Jablochkoff, and will now give some account of the experiments actually made at the Grands Magasins of the Louvre, and also of the note presented by M. Denayrouse to the Academy of Sciences on the 17th of April, 1877. At the Magasins the object was to increase the light in the Marengo Hall, which was supplied with eleven lustres, and also received light from the halls surrounding it. Around the Marengo Hall, at about two-thirds of the height, there is a gallery on which the electric lights were placed. Two "Alliance" machines worked six candles, and by an ingenious arrangement the candles when burned out were replaced by others, without causing a sensible diminution of the light. The candles were arranged in diffusing globes, and the light was projected forward by means of reflectors. Two sticks of Carré's carbons, 4 mm. in diameter and 12 cm. long, insulated with a thin plate of silicious matter, and fixed in two copper tubes, which were united by a plug of asbestos, formed the candles. A slip of carbon laid across the top of the two carbon sticks served to light them. It was difficult to judge of the intensity of the electric light, as the gas was not entirely extinguished, and the neighbouring galleries added their light also, but with a pocket photometer each candle was found to give about 20 to 25 Carcel burners. The irregularities were not great, but of tolerable frequency. A slight and continual flickering was perceptible in all the lights, arising from the nature of the carbons and changes of speed of the motor. An effect of a special kind, which was no doubt due to the ebullition of the silicious substance interposed between the carbons, gave a singing sound to the diffusing globe. We were told that the candles would last three-quarters of an hour; at the Louvre they were renewed every half hour. The advantages of this mode of lighting can only be decided by knowing the cost of machines, motor, &c., the expense of erecting them, and the cost of maintenance per hour for each unit of light. A comparison could then be made with the cost of other existing

p. 192

electric lights, such as those erected at M. Ménier's chocolate factory at Grenelle.

The labours of M. Jablochkoff have, from a purely scientific point of view, an undoubted value, as he has demonstrated that these voltaic arcs can be maintained in the circuit of a single current, and that two parallel carbons separated by a silicioue plate produce a light less intense, it ie true, than that of a regulator with ordinary retort carbons, but quite as regular and less intermittent. The possibility of dividing the electric light experimentally, or for purposes of scientific demonstration, was proved by M. Florent at St. Petersburg with Konn's lamp, but the novelty of the newer experiments is that the carbons are burned in the air, and not in a vacuum, as in M. Konn's arrangement. There is no doubt that M. Jablochkoff, with the active cooperation of M. Denayrouse, will succeed in making the light more economical, and in considerably reducing the large outlay which his system necessitates; but as far as the application of the light to industrial purposes is concerned, the experiment at the Magazins of the Louvre proves nothing whatever. In fact, the only inference to be drawn therefrom is that the cost of this new method of electric lighting is much higher than tbat of the old system.

The two "Alliance" machines and the six standards for carrying the candles employed in the Jablochkoff arrangement cost at least as much as six Gramme machines and six Serrin lamps. The six candles give 240 Carcel burners,*

[FOOTNOTE] * These figures must not be taken as absolute. Our estimate was 20 to 25 Carcel burners, and observations made independently by two other persons gave 22 and 30 Cancel burners. But as it is difficult to take exact measurements, we will reckon 40 burners to one Jablochkoff candle. Even if we double this number, the result of our comparison will not be altered to any appreciable extent.

whereas six Gramme machines with Gaudoin'a carbons give 3000 Carcel burners. Taking, then, the first cost of plant as equal, the system with regulators gives twelve times more light than that with candles.

Taking the horse-power absorbed by the two "Alliance" machines at a minimum, namely, 5 horse-power, two Gramme machines with the same power would produce 1000 Carcel

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burners, in place of the 240 burners given by the six Jablochkoff candles. In this respect the advantage is again considerably in favour of lighting by means of regalators. The superiority of the old system is established in the most convincing manner by comparing the consumption of carbons.

An electric candle costing at least half a franc lasts half an hour, being at the rate of 1 franc per hour for 40 burners and 12 1/2 francs for 500 burners. With ordinary carbons, the same quantity of light is produced at M. Ménier's for a quarter of a franc; the cost of the candles is therefore fifty times greater than that of regulator carbons. We cannot repeat too often our opinion that M. Jablochkoff will soon succeed in reducing in a certain degree the heavy expenses to which we have just drawn attention.

For instance, the "Alliance" machines are dear, but it is possible to manufacture them at a lower cost, and the candles can also be made more economically. The only fact which we insist upon is, that it is materially impossible to replace advantageously the regulators by candlea.

The experiment made at the Grand Magasins of the Louvre was very interesting; it attracted the public, and the journals spoke of it in terms of praise. If not absolutely practical, it yet deserves pnblic attention as being the germ out of which in future a great success may grow. In a word, neither a favourable nor an unfavourable conclusion can be deduced from this experiment, which is perhaps a step towards the solution, but certainly does not satisfactorily solve the problem. The difference of colour between the electric light and gas-light was plainly shown, but this difference was also observed some years ago on the Boulevard des Italiens, when M. Tessié du Motay made some experiments with the oxy-hydrogen light.

M. Denagrouse's note to the Academy related to the complete suppressing of the carbon in the production of the electric light. M. Jablochkoff conceived the idea of introducing into the cirenit of a magneto-electric machine the primary wire of a series of induction coils; in the secondary wire of each bobbin is placed a plate of kaolin, through which the induction sparks pass. The interposed plats of kaolin gets hot, reddens, and at last becomes

p. 194

luminous. Around the edge of the plate is placed a priming of a better conducting substance than the kaolin itself. By this arrangement M. Jablochkoff hoped to produce fifty lights with a single magneto-electric machine. The aspirations of MM. King, Lodyguine, Konn, Kosloff, and de Changy were of a like nature, and we wish M. Jablochkoff better success than his predecessors obtained.