On several occasions we have begged the English to finish this enormous scaffolding on top of which they have placed their electric lighthouse, and which disgraces the Champ de Mars with its emaciated frame. They did not do anything with it, and we must represent the English lighthouse as it remained. The mischief is that our neighbours had this beautiful work done by French workers.
Ah! if it had been a question of exhibiting a bundle of goods, the English would have thought of the preparation and the ornamentation. But a simple model of a scientific experiment, not intended for sale, what is the point of adorning or embellishing it? What does it matter that their lighthouse, with its finished ridge and its miserable frame, resembles a large reaper whose small head is carried by monstrous legs? what does it matter, as long as its flashes shine from afar?
Does the lighthouse at Roches-Douvres, with its elegant iron frame and painted polygonal walls that attract rather than repel the eye, light up better than the English lighthouse, which is so unsightly to the eye? That is the whole question for the English, practical people. Well, this time the practical people made a false calculation of economy, whereas the prodigal French calculated as sensible people. - At the end of the Exhibition, the French lighthouse will have cost only the cost of its installation on the Champ de Mars, since it will be transported to the Roche-Douvres islet, where it will have its final destination. On the other hand, the English lighthouse will have to be dismantled, without being able to use its remains; and if, as I suppose, the English want to use the focal system on their coasts that they are exhibiting at the Champ de Mars, they will have to incur expenses that we will no longer have to make. Where will the savings have come from?
Yes! in our experiments with electric lighthouses we have thought of the pleasure of visitors, which the English have so greatly disdained. The French electric lighthouses flood the Champ de Mars and the Trocadero with their luminous waves: the English electric lighthouse projects its solitary flashes far and wide. So much for the pleasure; as for the expense, I consider that the French installation has cost much less than the English one.
Mr. Holmes has devised a system of telephone signals, driven by steam, and therefore very expensive, a system which I mentioned a few days ago. We have installed on the bank, in a turret barely 8 metres high, a bell which achieves the same result as Mr. Holmes' system, that of warning the ship in distress, which the lights of the lighthouse can no longer illuminate.
M. Guizot said of the experiment that it was "a flame that does not shine from afar, and that it only illuminates well those whom it consumes. "Experience is therefore the exact opposite of the light of lighthouses, which only shines well from a distance. This is why telephone signals were invented, to warn sailors who were too close to see, but close enough to hear, of the danger.
As for the opacity of the atmosphere, the intensity of electric light is better at combating its inconveniences than all telephone signals. And in this respect the low projections of French electric lighthouses are more convincing than Mr. Holmes' monstrous book.
To return to the English lighthouse, it would have been possible to build with timber a structure that would not have stood out among the elegant and rich oriental establishments in the vicinity. There is at Pontailhac, on the Gironde, near Royan, a lighthouse entirely made of framework which is of a beautiful effect, and which the English must know: they would only have had to take their model from it.
But they were in a hurry: the Roche-Douvres lighthouse prevented them from sleeping; and, having no time to study a model installation, they ran to the result, which was to produce electric flashes as intense and as high as those of the oil lamps of the French lighthouse.
At the foot of the pylon, there is a small building on which one reads: Electric machine for the service of the lighthouse. The door remains closed, but it is possible for us to speak of the apparatus which this establishment conceals.
The two large machines which serve to produce electric current, carefully wrapped up, moreover, as if they were bound to keep a secret, are built on the principle of induction currents, discovered in 1831 by Faraday. Although we have already spoken of this in connection with French electric lighthouses in our fourth issue, page 50, we feel we must return to it in connection with the English lighthouse.
If a coil of copper wire wound round a cylinder of soft iron is rapidly moved towards or away from a fixed magnet, electric currents are instantly developed in the wire of this moving coil.
It is by taking advantage of this principle that very energetic currents have been obtained by moving coils about an axis of rotation, so that the ends of these coils move briskly towards or away from the fixed magnet poles. Pixii and Clarke had already constructed devices of this kind, long known in the physics cabinets. But there is a long way to go from these primitive experimental machines to the large industrial machines which today produce electricity in a safe, regular and economical way, such as we find them exhibited at the Champ de Mars. It is to Messrs. Joseph Van Malderen, in France, and Holmes, in England, that we owe the principal improvements made in magneto-electric machines.
From Faraday's principle, stated above, it follows that copper wire coils, under the influence of opposite poles, produce alternating currents. And it is here that the essential difference between the English and the French system becomes apparent.
In the English machine, the currents are picked up by a switch which rectifies them and makes their direction constant; in the French machine, the switch, which is a cause of loss as a result of the release of sparks which accompanies each interception of current, this organ, I say, does not exist; and, by its suppression, M. Joseph Yan Malderen has made a notable improvement. I base this conclusion on the printed catalogue of the Ministry of Public Works, where I read that the experiments made in Paris, in 1805, on the English electro-magnetic machine, fitted with a switch, and the French machine, established that the useful effect of the former was 45 hundredths less than that of the latter.
I would like, by the essential details I give, to communicate to our readers the desire to go deeper into this very interesting subject, and which the Exhibition of 1867 provides us with the opportunity to tackle.
The magneto-electric apparatus of the English Lighthouse is set in motion by a small stationary steam engine, the Allen system, which is fed from the large boilers near Galloway.
The electric current is directed by means of conductor wires to the top of the lighthouse; the regulator carries two oppositely pointed carbon rods, between which the light is formed. The light is reflected back to the horizon by a lenticular apparatus with a fixed light from the system of our immortal Fresnel.
I do not believe, after what I have said in the fourth issue already mentioned, that I should dwell any longer on the production of electric light and on the comparison of electric headlights with oil headlights. I will only remind you that in electric lighthouses, in England as in France, there is a double set of machines to ensure the continuity of the light, in case one of the mechanisms should fail, and above all to be able to double the intensity of the light in foggy weather.
In the ordinary state of atmospheric transparency, the oil lighthouses carry as far as their elevation above sea level allows. Under these conditions, the electric lighthouse does not light any better or further; even when the opacity of the air increases, its loss of light is relatively greater than that of the oil lighthouse. But when thick fog obscures the horizon, the electric lighthouse regains all its advantages: its focal lamp then receives the currents of its two coupled magneto-electric machines, which give it incomparable power.
Those who see the flashes of the English electric lighthouse and those of the French oil lighthouse in the distance will not distinguish any difference in intensity. Those who are familiar with the experiments made in 1865 on the two English and French electric systems will not change their opinion in the presence of the disgraceful appeal made by our neighbours at the Champ de Mars.
©L'Exposition Universelle de 1867 Illustrée