Lightships and Lighthouses. Frederick Arthur Ambrose Talbot
it could not compete with the lard-oil, and suggested that the latter should be employed in preference to the colza. The Government agreed, but, to compensate the company for its trouble, purchased the plant which the latter had laid down.
The advances in the processes for refining petroleum, and the exploitation of the extensive resources of the latter, led to “earth-oil,” in some form or other, being employed for lighthouse purposes. The attempt was facilitated by the invention and improvement of the Argand burner, whereby a brilliant white annular sheet of flame is produced. Various lighthouse engineers devoted their attention to the improvement of this burner in conjunction with paraffin. Their results were completely successful, and at last paraffin became universally utilized as the cheapest and most efficient illuminant known.
The general method of feeding the lamps was to pump the oil from a low level to the burner, thereby producing practically a pressure-feed system in preference to the capillary action which is used in the ordinary household lamp. By increasing the number of rings the intensity of the flame was increased, until at last it was thought that with this development perfection had been attained so far as lamps were concerned.
Then came another radical revolution. The invention of the incandescent gas mantle by Dr. von Auer, and the complete change that it wrought in connection with gas lighting, induced lighthouse engineers to experiment in this field. As they could not use coal-gas, they devoted their investigations to the perfection of a gas from petroleum, which should be capable of combustion with the incandescent burner. Many years were devoted to these experiments, and many petroleum vapour systems were devised. One of the best known, most successful, and most scientifically perfect, is the Chance incandescent light. This burner is used in many of the most powerful lights of the world and has given complete satisfaction. The mantle varies in size with the size and type of the light, ranging from 35 to 85 millimetres in diameter, the latter, in conjunction with a hyperradial apparatus, producing a light exceeding 1,000,000 candle-power.
By courtesy of Messrs. Chance Bros. & Co., Ltd.
THE HYPERRADIAL APPARATUS FOR THE MANORA POINT LIGHT, KARACHI, INDIA.
Of 1,330 millimetres focus, this is the most powerful and largest lighthouse apparatus made.
Not only was a far more powerful light obtained in this manner with the assistance of the petroleum vapour burner and incandescent mantle, but the cost of maintaining the light was reduced, owing to the great economy in oil consumption that was effected thereby, the largest mantle and burner—85 millimetres—burning only 2½ pints of oil per hour. The light thus obtained, while being vastly superior to that derived from a six-wick oil-burner, enables a saving of nearly £48, or $240, per annum to be recorded, taking the cost of the petroleum at 1s., or 25 cents, per gallon delivered to the lighthouse.
While petroleum is generally used, some countries have adopted other oil fuels for small permanent lights. Thus, in Germany compressed oil-gas, water-gas associated with benzine vapour, and Blau liquid gas, are utilized. The last-named is coming very extensively into vogue, also, in Holland, Denmark, and Austria. Blau gas has the advantage that it can be transported in small steel tanks under extremely high pressure—up to 100 atmospheres, or approximately 1,400 pounds per square inch. It is an extract of oil-gas produced at a low pressure in the gas retorts, and then compressed so severely that it liquefies. The fuel, as it is drawn from the cylinder in which it is stored, has the pressure reduced by means of a valve, so that it reaches the burner in a gaseous form at a pressure equivalent to that of the coal-gas used in private houses, and is burned in the same way with an incandescent mantle. The advantage of this method lies in the facility with which large volumes of gas may be transported, a steel cylinder containing 7,500 cubic feet weighing only 132 pounds. It is also inexpensive, a bottle of the foregoing capacity costing only 12s. 6d., or $3. In some cases the incandescent mantles, the average life of which is about a fortnight, are of large diameter, running up to 100 millimetres, or about 4 inches.
Recently Mr. Gustaf Dalén, of the Gas Accumulator Company of Stockholm, the inventor of the Dalén flasher and sun-valve, which are described elsewhere, has introduced a new illuminant, which is coming into vogue, especially on the Continent. This is called “Daléngas,” and is a mixture of 9 per cent. dissolved acetylene and 91 per cent. atmospheric air. Here the dissolved acetylene gas is conducted from a storage reservoir or high-pressure gas cylinder, of special construction, to a governor, where the pressure is reduced, and then to the mixing apparatus, where the acetylene gas is associated with the air in the above proportions. The idea of this combination and method is to enable an acetylene gas mixture to be used with the ordinary incandescent mantles.
By courtesy of Messrs. Chance Bros. & Co., Ltd.
FIRST ORDER TRIPLE FLASHING LIGHT OF 920 MILLIMETRES FOCAL DISTANCE FOR CHILANG LIGHTHOUSE, CHINA.
The advantage of the Daléngas, according to present experience, is the increased candle-power that is obtainable as compared with other systems, the superiority being about 75 per cent. under ordinary conditions. With the largest Fresnel lenses a lighting power of 200,000 Hefner candle-power is secured, while with revolving lenses of the latest type a beam of 3,000,000 candle-power can be obtained. The flame is small, and thus becomes concentrated more in the focus of the lens, so that the divergence of the light may be diminished if desired. When a light of a certain range is to be installed, the optical apparatus can be made smaller for Daléngas than for other illuminants, and the cost is reduced correspondingly. Similarly, if the system is introduced into an existing light, the latter can be made appreciably more powerful, without changing the optical apparatus or affecting the divergence.
In this system the gas is conducted into the lens apparatus from above, and the lighting arrangement is quite independent of, and does not interfere in any way with, the revolving apparatus, while the time spent in changing the mantle is less than half a minute.
All combustible gases, mixed with air in certain proportions, may produce more or less violent detonations when fired. But the quantity of mixed gas in this instance is confined in the length of piping between the burner and the mixing apparatus, and this quantity is so small that an explosion cannot be dangerous. In fact, all such danger has been guarded against completely—is, indeed, impossible in any circumstances.
Electric light has been adopted in one or two cases; but while the foremost authorities agree that it throws the best, most brilliant and most powerful beam of light, the system is generally impracticable on account of its great cost. When tests with this light were made some years ago in comparison with the light thrown from oil burners, it was claimed that the latter, owing to its reddish-yellow tinge, was the most suitable from the all-round point of view, and that it could penetrate to a greater distance in foggy weather. I have been informed by several authorities, who have gone more deeply into this question since, that this is a fallacy, and that the advantage rests completely with electric light. Experience in Germany, which has two magnificent electric lighthouses, and in Scotland, certainly supports this contention, and I have been assured that the sole reason why electric lighting has not been adopted more widely is the heavy cost, both of installation and of maintenance. When electric lighting is rendered cheaper and is brought more to the level of existing lighting arrangements, one may expect another complete change in lighthouse practice. In this direction, as explained in another chapter, the Germans have carried out practical experiments in their characteristic manner, and have brought the cost of maintaining a most powerful electric light to the minimum.
One very great advantage of the electric light is the ease with which the power of the beam may be increased during thick weather, so as to secure penetration to the greatest distance, and decreased to suit easier conditions in clear weather.
This point raises the question, “From how far can a light be seen out at sea?” This factor is influenced by climatic conditions, and also by the curvature of the earth. The higher the light, or the spectator, or both, is elevated above the water, the greater the distance from which the light can be seen. The table on p. 52,