THE LIGHTING OF RAILWAY CARS.

IN the well-appointed passenger trains of to-day, travelling is a pleasure as compared with the tedious journeys of a few decades since. The railways are on the alert to meet the requirements of a discriminating public, not only caring for their safe and prompt transportation, but also catering to their demands for comfort and even luxury. A large part of travel must be done during hours of artificial lighting, especially by business men, who constitute the majority of passengers, and who wish to do their travelling as much as possible outside business hours. The problem of securing satisfactory light in the cars is therefore one of considerable importance.

In the early days, when people were accustomed to the light of flickering candles, no better light was desired on trains. At first the trips were short and were made only during the daylight hours. The first artificial lighting of railway cars began nearly three-quarters of a century ago, passengers sometimes furnishing their own candles or oil lamps on long journeys. Candles, furnished by the company and placed in convenient pockets, were gradually displaced by lamps burning animal, vegetable, or mineral oils. The oil lamp was developed until it gave quite a respectable light, although accompanied by disagreeable and expensive features, and the suspicion that fires in connection with wrecks. were aggravated, if not caused, by oil lamps quite as often as by stoves.

As early as 1856, experiments were made on the Chicago and Galena Railway with the use of compressed city gas for car lighting. Coal gas loses much of its illuminating power when compressed, and has therefore been practically abandoned for train use. In 1867, Julius Pintsch, of Berlin, began experimenting with various gases, and found that gas made by heating oil to a high temperature would stand compression with little loss of illuminating power. He succeeded in building up a business of great magnitude. During the last few years, acetylene gas made from calcium carbide, a product of the electric furnace, has been applied to car lighting with more or less success. Incandescent electric lamps were first used for train lighting in 1881, and are now used in many of the best trains in all countries.

Each of the old methods of car lighting has certain features which are objectionable to the travelling public, to railway men, or to both. The first requirement in any satisfactory method is safety. The devices for burning oil and gas have been brought to a high stage of progress. Yet, with any illuminant requiring a flame, there is at least a possibility of fire risk. In the case of gas, there is the added possibility that pipes may become broken and allow the gas to escape and mingle with the air, until an explosive mixture is formed. The results of the explosion of such a mixture would not be pleasant to contemplate.

The worst features of oil and gas are the products of combustion. Oil and gas lights not only cause a large amount of heat, which adds to the discomfort of summer travel, but they use up the oxygen of the air faster than do the passengers. The products of combustion are generally carbonic acid gas, water vapor, and heat. When the lights do not burn properly, they may give off more or less of a poisonous gas known as carbon monoxide. The presence of the carbonic acid gas and of the water vapor has a tendency to make a person feel drowsy and dull. The water vapor adds to the discomfort by reducing the evaporation from the skin. A large part of the waste from the body is eliminated through the skin by insensible perspiration, the evaporation of which cools the body. As the air becomes saturated with water vapor, evaporation from the body diminishes, and one soon becomes hot, drowsy, and uncomfortable. The principal function of the fan is not so much to cool the air as to blow fresh air upon a person, and so increase the evaporation from the body, and thereby indirectly cool it. The electric fan in dining and parlor cars is a grateful luxury as it causes the air to circulate, even though it be warm, and thus continually brings near the skin air that is less fully saturated with moisture.

The degree of emphasis to be placed upon this consideration may be inferred from a few figures. For illuminating various kinds of American passenger cars, the light varies from the equivalent of that given by about forty candles to that given by 1,200 or 1,500 candles. The ordinary car has an illumination equal to that of about 170 candles. The consumption of oxygen and the products of combustion in the lamps giving that amount of light may be compared directly with the presence of a number of passengers; the candles being equal to about 115 adults, oil lamps being equal to about eighty adults, and gas being equal probably to about twenty-five adults. The above comparison makes no allowance for the additional discomfort of dirty lamps, which smoke and smell.

A great objection to the oil lamp is its liability to smoke; and another is its liability to leak oil on the carpets and upon the clothes or baggage of passengers. It was stated, several years ago, that it was costing the Pullman Company about $200,000 annually to replace carpets and other furnishings injured by oil lamps; no record being available, however, of the damage to the property of passengers.

When the incandescent electric lamp approached a commercial form, in 1879, its advantages were quickly recognized. Experiments looking toward its use on railway cars were begun almost before the first central station for stationary lighting was in operation. In spite of the frailties of the early lamp and the limited sources of electricity then available, the London, Brighton and South Coast Railway in England began in November, 1881, to operate electrically lighted trains, and has continued this method of illumination until the present time, making improvements from time to time as experience dictated. Soon after this trial began, other roads, in nearly every country, followed; and to-day the number of cars lighted by electricity runs up into the tens of thousands, not counting the myriads of trolley cars, which are lighted and propelled from the same source of power. A history of the development of electric lighting for railway cars would make an interesting study for railway officials and others who desire to keep fully posted in this branch of electrical work.

As is generally known, the light of an incandescent electric lamp comes from a slender carbon filament in a vacuum maintained within closed glass bulb; this filament being heated to a high temperature by an electric current. So little heat escapes to the outside that the lamp may be placed with safety in almost any location desired. There is no open flame which may set fire to combustibles near by, and the external temperature is so low that only actual contact for a considerable time will carbonize or ignite the most inflammable material. It heats the atmosphere to a very limited extent only, and does not vitiate it in the least, there being no combustion. The lamp may be lighted without a match by the simple turning of a key, and may be extinguished with equal facility and safety. With proper care on the part of those in charge, there will be no fluctuation in the light, neither streaks nor shadows. Experience has shown methods of construction and operation which make the electric light safe as a fire risk; and the voltage used is so low that it is impossible to receive a shock of any consequence.

When the electric berth lamp was introduced it met with instant success. A passenger who has enjoyed the luxury of a cool light at

his shoulder, available at any time during the night, without any disturbance, always seeks a sleeping-car with electric lights. The travelling public is satisfied with nothing less; and to-day no train can be called thoroughly modern and up-to-date unless it can advertise berth lights. The latter are electric, of course, for no other kind has appeared. Along with the berth lamp is the possibility of having electric fans to keep the air in circulation. Another advantage which appeals to ladies is the comfort of heating a curling-iron without the nuisance of an alcohol lamp, so trying and dangerous in the cramped quarters usually allowed for ladies' dressing-rooms. On trains equipped with storage batteries, each compartment and each dressing-room may be furnished with electric heaters, always ready for use by simply inserting the tongs.

Power for operating the electric lamps and other devices may be obtained from storage batteries carried underneath the car, from dynamos, or from a combination of the two. The storage battery consists of a number of lead plates immersed in diluted sulphuric acid. When a current is sent through the battery from an outside source, certain chemical changes take place, which make the plates electrically different; so that when the circuit is provided they will cause a current to flow through. There is no storage of electricity as such, the energy of the charging current being changed into chemical energy, which is stored and later is retransformed into electrical energy.

The dynamo, often called an electrical generator or a dynamo electric machine, is a device for changing mechanical energy into electrical energy; it is based upon the interrelations of electricity and magnetism. For train lighting, the dynamo is driven by a steam engine in the baggage car, or it is belted to the axle. For the engine-driven dynamo steam is obtained from the locomotive; and provision must be made for supplying light when the locomotive is changed at division points. There is likely to be some vibration from the engine throughout the train, which, however, is noticeable only when the train is standing still.

With the axle system provision must be made for lighting the train when standing and also when running at too low speed for the dynamo to operate. The storage battery furnishes the simplest means of supplying light at such times; suitable devices being arranged to transfer the lights from dynamo to battery or vice versa, as required. In connection with the axle-driven dynamos, the batteries are charged from the dynamo on the car, either while the lamps are lighted, or during the

day, or at both times. Batteries used as auxiliaries to engine-driven dynamos are charged either en route or at the terminals, while the train is being cleaned and inspected for the next trip. Batteries used for lighting without any dynamo on the train must be charged at the terminals of the road.

The choice of an electric-lighting system best adapted to a given train or to a given road involves a number of technical considerations which require careful investigation. It may be said in general, however, that the storage battery without any dynamo on the train is suitable for trains which are not more than one day away from a source of charging current; that the system of engine with dynamo in the baggage car is suitable for solid trains going through to their destination, without any changes in make-up; and that the axle-lighting system finds a field almost its own in the case of through trains on runs several thousand miles long, and on trains which are split up by having cars added or removed en route, while it can compete in point of economy and good service on trains for which the other systems are suitable.

Comparing the different sources of light, passengers prefer gas to oil, and electricity to gas, provided the electric lights are properly taken care of and are reliable. Since experiments with electric lights on trains have been made from the time when the electrical art was in an early stage of development, it is not surprising that some of the early attempts were not as conspicuously successful as they were expensive. The compressed-gas system was brought to a reliable and commercially successful stage ten years before the electric incandescent lamp was ready, and the gas interests made good use of their opportunity to preempt the field. After much expensive development, and in the face of many discouragements, the advocates of electric light for train use have overcome nearly all obstacles; and to-day the electric light is recognized as the only thing for the best service. The modern apparatus is developed to such a state of reliability and perfection that it is now possible for the railways to purchase electric-lighting outfits, or to secure them on a rental basis at moderate cost and guaranteed by ample capital. Now that the electric light has won its standing with the railways, the public may expect a rapid adoption of this admirable source of light and ventilation. GEORGE D. SHEPARDSON.