Oil-lamps have been devised in which the oil is burned as a spray ejected by air-pressure.  These burn with a large flame; however, a serious feature is the escape of considerable oil which is not burned.  These lamps are used in industrial lighting, especially outdoors, and possess the advantage of consuming low-grade oils.  They produce about 700 to 800 candle-power hours per gallon of oil.  Lamps of this type of the larger sizes burn with vertical flames two or three feet high.  The oil is heated as it approaches the nozzle and is fairly well vaporized on emerging into the air.  The names of Lucigen, Wells, Doty, and others are associated with this type of lamp or torch, which is a step in the direction of air-gas lighting.

During the latter part of the nineteenth century numerous developments were made which paralleled the progress in gas-lighting.  Experiments were conducted which bordered closely upon the next epochal event in light-production—­the appearance of the gas mantle.  One of these was the use of platinum gauze by Kitson.  He produced an apparatus similar to the oil-spray lamp, on a small and more delicate scale.  The hot blue flame was not very luminous and he attempted to obtain light by heating a mantle of fine platinum gauze.  Although these mantles emitted a brilliant light for a few hours, their light-emissivity was destroyed by carbonization.  After the appearance of the Welsbach mantle, Kitson’s lamp and others met with success by utilizing it.  From this point, attention was centered upon the new wonder, which is discussed in a later chapter after certain scientific principles in light-production have been discussed.

The kerosene or mineral-oil lamp was a boon to lighting in the nineteenth century and even to-day it is a blessing in many homes, especially in villages, in the country, and in the remote districts of civilization.  Its extensive use at the present time is shown by the fact that about eight million lamp-chimneys are now being manufactured yearly in this country.  It is convenient and safe when carelessness is avoided, and is fairly free from odor.  Its vitiation of the atmosphere may be counteracted by proper ventilation and there remains only the disadvantage of keeping it in order and of accidental breakage and overturning.  The kerosene lantern is widely used to-day, but the danger due to accident is ever-present.  The consequences of such accidents are often serious and are exemplified in the terrible conflagration in Chicago in 1871, when Mrs. O’Leary’s cow kicked over a lantern and started a fire which burned the city.  Modern developments in lighting are gradually encroaching upon the territory in which the oil-lamp has reigned supreme for many years.  Acetylene plants were introduced to a considerable extent some time ago and to-day the self-contained home-lighting electric plant is being installed in large numbers in the country homes of the land.

VI