There is no more eager contest than that which has been going on for some time between gas and electricity. Which of these two systems of lighting will triumph? Will electricity suppress gas, as gas has dethroned the oil lamp? A few years ago, the answer to this question would not have been doubtful, and it seemed as if gas in such contest must play the role of the earthen pot against the iron one. At present the case is otherwise.

The Auer burner has re-established the equilibrium, and the Denayrouse burner is perhaps going to decide the fate of electricity.

As naturalists say, the function creates the organ, and it is truly interesting to observe that in measure as the need of an intenser and cheaper light grows with us, science makes it possible for us to satisfy it by giving us new systems of lighting or by improving those that we already have at our disposal.

What a cycle traversed in twenty years! What progress made! Let us remember that the electric light scarcely became industrial until the time of the Exposition (1878), and that the Auer burner obtained the freedom of the city only five or six years ago. Is there any need of recalling the advantages of these two lights? In the first, a feeble disengagement of caloric, automatic lighting and a steadier light; in the second, a better utilization of the gas, which gives more light and less heat.

A description of the Auer burner will not be expected from us. It is now so widely employed as to render a new description useless. As an offset we think that our readers will be more interested in a description of the Denayrouse burner, the industrial application of which has but just begun. This burner has been constructed in view of the best possible utilization of the gas, in approaching a complete theoretical combustion. In order that it may give its entire illuminating power, gas, as we know, must be burned in five and a half times its volume of air. In the Denayrouse burner the gas burns in four and four-tenths its volume of air. The result reached is, consequently, very appreciable.

SECTION OF THE LAMP
A, entrance for the air; G, entrance for the gas; V, mixer; M, electric motor.

The apparatus consists essentially of a bronze or brass box in which revolves a fan keyed upon an axle that passes through the box. The axle is revolved by means of a small electro-magnetic machine mounted upon one of the external sides of the box. The motor may also be a hydraulic or compressed air one. Upon the axle is arranged a speed regulator. The air enters at the bottom of the box and the gas at the center. The exit of the mixture takes place through a chimney arranged at the top and to which is fixed a luminous mantle. The apparatus operates as follows: The motor causes the fan to make about 1,200 revolutions a minute. There is thus formed a strong draught of air, which mixes with the gas that enters at the side. The ignition occurs at the upper aperture of the chimney.

Although in this competition of gas and electricity the intensity of the light and, its quality are important factors, it is certain that what will decide the victory will be the price. This is why we are going to establish the net cost of the different lights; for, although up to the present the contest has seemed to be limited to gas and electricity (oil and kerosene not being capable of having any other pretension than to preserve their position), a new competitor - acetylene - will perhaps soon put gas manufacturers and electricians in accord, to the great benefit of the public, by furnishing a brilliant light at a price that defies competition.

THE DENAYROUSE LAMP

In all systems of lighting, save electricity, the unit of light is the carcel. This represents the light produced for one hour by 10 wax candles, or, better still, it is the illuminating power given by the combustion of 42 grammes of pure colza oil for one hour in what is called a carcel lamp.

In electricity we count by watts. The watt, like the kilogrammeter, of which it represents nearly a tenth, is not a unit of light, but a unit of energy. What is called a kilogrammeter is the force capable of lifting 1 kilogramme to 1 meter in height during 1 second. Further along we shall estimate the watts in carcels.

This stated, let us ascertain the net cost of the unit of light in each system of lighting. We shall take as a basis the Paris prices, which are generally higher than those of other countries, owing to taxes, and shall confine our researches to the eight following systems:

Electricity (incandescent and arc lamps), gas (butterfly, Auer and Denayrouse burners), lamp oil, kerosene and acetylene.

1. Oil Lamp. - This method of lighting has become more and more neglected because it is the most troublesome. The mean price of the kilo is 1.6 francs. As the carcel hour consumes 42 grammes, it consequently amounts to 0.06, say 6 centimes.

2. The Incandescent Lamp. - In the scale of prices one of the oldest processes of lighting is closely followed by one of the most recent - the incandescent lamp. We shall base our calculations upon the Edison 16 candle electric lamp, which is the one most widely used. In this it takes 35 watts to obtain a carcel. As the hectowatt, the mean price of which is 15 centimes, gives approximately 3 carcels, the price of the carcel will, consequently, be 5 centimes.

3. Gas. - Gas, with the butterfly burner, burns from 125 to 130 liters to furnish the carcel. As the price of a cubic meter is 30 centimes, the carcel will cost 0.39, that is to say, 4 centimes.

4. Kerosene, the decline of which is perhaps beginning, costs about 0.75 centime per kilo. The consumption per carcel is nearly 40 grammes. It amounts, therefore, to 3 centimes.

5. The arc lamp is of very varied model. We shall take as a type those used for lighting the large boulevards. They are of 8 amperes and 50 volts; that is to say, of 4 hectowatts, and are presumed to give an illuminating power of 300 carcels. The carcel is consequently obtained with 13 watts and its net cost is 0.0195, or, approximately, 2 centimes.

6. Acetylene. - This new system of lighting has hardly as yet made its exit from the laboratory. So we must not be greatly astonished at the variations in the price at which it is claimed that it can be obtained on the two sides of the Atlantic. As a kilo of carbide of calcium gives 300 liters of acetylene, and as the minimum price of the carbide is 40 centimes per kilo in France, a cubic meter of the gas costs 1.35 franc. As it requires about 7.5 liters to give the carcel, the latter will consequently amount to 0.01; say 1 centime.

7. The Denayrouse Burner. - This burns nearly 300 liters of gas to produce 30 carcels, normally. As the photometric experiments are recent, let us suppose that it gives but 25 carcels. As 300 liters of gas represent an approximate expense of 10 centimes, we shall obtain the carcel at the price of 0.004, or at less than half a centime.

8. The Auer Burner. - This burns nearly 115 liters of gas to produce 5 carcels. The expense per carcel, with the cubic meter of gas at 30 centimes, is therefore 0.0069; say 0.7 of a centime.

Finally, in the United States, thanks to particularly favorable hydraulic installations, it is claimed that it is possible to produce acetylene at a very low price, say at 33 centimes per cubic meter. Under such conditions, the carcel would cost no more than 0.0025, say ¼ of a centime. It seems, however, that these are hypotheses as yet. If they chanced to be realized, it is certain that acetylene would be the light of the future; but those who are best informed in the matter assert that they never will be realized.

In order to establish still more accurately the net cost of each of these systems of lighting, it is necessary to take into account the wear of the mantles of the incandescent lamps and the carbons of the arc ones. As regards these latter, it is customary to estimate the wear of the carbons at 8 centimeters an hour.

As for the mantles, we shall base our calculations upon the data furnished by those interested; say 1,000 hours for the Edison lamp, 1,200 for the Auer burner and 400 hours for the Denayrouse burner. It must be remarked that in practice such duration generally drops to a half. The price of the mantles in these different systems is approximately 2.5 francs.

1. As the Edison 16 candle lamp gives 1.6 carcels and its filament burns 1,000 hours, the wear will increase the price of the carcel by 0.0015.

2. As the Auer burner gives 5 carcels and its mantle burns 1,200 hours, the wear will increase the price of the carcel by 0.0004.

3. As the Denayrouse burner gives 25 parcels, and its mantle burns but 400 hours, the wear will increase the price of the carcel by 0.0002.

Finally, if we compare the butterfly, Auer and Denayrouse burners with each other, in taking into account the cost of replacing the mantles of the two latter and the actuating of the Denayrouse burner, we find the following figures per carcel hour:

Butterfly burner,	consumption	0.04
Auer burner,	consumption	0.0069
wear of mantle	0.0004
Denayrouse burner,	consumption	0.04
wear of mantle	0.0002
expense of motor	0.0003

Say	4	centimes	per	carcel hour	Butterfly	burner.
	0.7	"	"	"	Auer	"
	4.5	"	"	"	Denayrouse	"

For the same sum, the Auer burner, therefore, burns six times more and the Denayrouse nine times more than the butterfly. These figures may give an idea of the surprising intensity of the Denayrouse light.

Upon the whole, if the experiments that are being made publicly at this moment confirm the data of the laboratory, the Denayrouse burner will be destined to play a considerable role in the lighting of public gardens, streets and buildings, for the very intensity of the light that it gives renders it unfitted for private use. Moreover, it must not be forgotten that it requires a motor to actuate its fan, and everyone has not the necessary motive power in his house.

This New Burner Will Likewise Prove Very Valuable For The Righting Of Theaters

L'Illustration.