Part 8

The ordinary lamp consisting of a wick which draws up the mineral oil and feeds it to a flame is efficient and fairly free from danger. It requires care and may cause disaster if it is upset, but it has been blamed unjustly in many accidents. A disadvantage of the kerosene lamp over electric lighting, for example, is the relatively greater possibility of accidents through the carelessness of the user. This point is brought out in statistics of fire-insurance companies, which show that the fires caused by kerosene lamps are much more numerous than those from other methods of lighting. If in a modern lamp of proper construction a close-fitting wick is used and the lamp is extinguished by turning down and blowing across the chimney, there is little danger in its use excepting accidental breakage or overturning.

In oil-lamps at the present time mineral oils are used which possess flashing-points above 75 deg.F. The highly volatile components of petroleum are dangerous because they form very explosive mixtures with air at ordinary temperatures. A mineral oil like kerosene, to be used with safety in lamps, should not be too volatile. It is preferable that an inflammable vapor should not be given off at temperatures under 120 deg.F. The oil must be of such physical characteristics as to be drawn up to the burner by capillarity from the reservoir which is situated below. It is volatilized by the heat of the flame into a mixture of hydrogen and hydrocarbon gases and these are consumed under the heat of the process of consumption by the oxygen in the air. The resulting products of this combustion, if it is complete, are carbon dioxide and water-vapor. For each candle-power of light per hour about 0.24 cubic foot of carbon dioxide and 0.18 cubic foot of water-vapor are formed by a modern oil-lamp. That an open flame devours something from the air is easily demonstrated by enclosing it in an air-tight space. The flame gradually becomes feeble and smoky and finally goes out. It will be noted that a burning lamp will vitiate the atmosphere of a closed room by consuming the oxygen and returning in its place carbon dioxide. This is similar to the vitiation of the atmosphere by breathing persons and tests indicate that for each two candle-power emitted by a kerosene flame the vitiation is equal to that produced by one adult person. Inasmuch as oil-lamps are ordinarily of 10 to 20 candle-power, it is seen that one lamp will consume as much oxygen as several persons.

In order that oil-lamps may produce a brilliant light free from smoke, combustion must be complete. The correct quantity of oil must be fed to the burner and it must be properly vaporized by heat. If insufficient oil is fed, the intensity of the light is diminished and if too much is available at the burner, smoke and other products of incomplete combustion will be emitted. The wick is an important factor, for, through capillarity, it feeds oil forcefully to the burner against the action of gravity. This action of a wick is commonly looked upon with indifference but in reality it is caused by an interesting and really wonderful phenomenon. Wicks are usually made of high-grade cotton fiber loosely spun into coarse threads and these are woven into a loose plait. The wick must be dry before being inserted into the burner; and it is desirable that it be considerably longer than is necessary merely to reach the bottom of the reservoir. A flame burning in the open will smoke because insufficient oxygen is brought in contact with it. The injurious products of this incomplete combustion are carbon monoxide and oil vapors, which are a menace to health.

To supply the necessary amount of oxygen (air) to the flame, a forced draft is produced. Chimneys are simple means of accomplishing this, and this is their function whether on oil-lamps or factories. Other means of forced draft have been used, such as small fans or compressed air. In the railway locomotive the short smoke-stack is insufficient for supplying large quantities of air to the fire-box so the exhausted steam is allowed to escape into the stack. With each noisy puff of smoke a quantity of air is forcibly drawn into the fire-box through the burning fuel. In the modern oil-lamp the rush of air due to the "pull" of the chimney is broken and the air is diffused by the wire gauze or holes at the base of the burner. These metal parts, being hot, also serve to warm the oil before it reaches the burning end of the wick, thus serving to aid vaporization and combustion.

The consumption of oil per candle-power per hour varies considerably with the kind of lamp and with the character of the oil. The average consumption of oil-lamps burning a mineral oil of about 0.80 specific gravity and a rather high flashing-point is about 50 to 60 grams of oil per candle-power per hour for well-designed flame-lamps. Kerosene weighs about 6.6 pounds per gallon; therefore, about 800 candle-power hours per gallon are obtained from modern lamps employing wicks. Kerosene lamps are usually of 10 to 20 candle-power, although they are made up to 100 candle-power. These luminous intensities refer to the maximum horizontal candle-power. The best practice now deals with the total light output, which is expressed in lumens, and on this basis a consumption of one gallon of kerosene per hour would yield about 8000 lumens.

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.

EARLY GAS-LIGHTING

Owing to the fact that the smoky, flickering oil-lamp persisted throughout the centuries and until the magic touch of Argand in the latter part of the eighteenth century transformed it into a commendable light-source, the reader is prepared to suppose that gas-lighting is of recent origin. Apparently William Murdock in England was the first to install pipes for the conveyance of gas for lighting purposes. In an article in the "Philosophical Transactions of the Royal Society of London" dated February 25, 1808, in which he gives an account of the first industrial gas-lighting, he states:

It is now nearly sixteen years, since, in a course of experiments I was making at Redruth in Cornwall, upon the quantities and qualities of the gases produced by distillation from different mineral and vegetable substances, I was induced by some observation I had previously made upon the burning of coal, to try the combustible property of the gases produced from it....

Inasmuch as he is credited with having lighted his home by means of piped gas, this experimental installation may be considered to have been made in 1792. In his first trial he burned the gas at the open ends of the pipes; but finding this wasteful, he closed the ends and in each bored three small holes from which the gas-flames diverged. It is said that he once used his wife's thimble in an emergency to close the end of the pipe; and, the thimble being much worn and consequently containing a number of small holes, tiny gas-jets emerged from the holes. This incident is said to have led to the use of small holes in his burners. He also lighted a street lamp and had bladders filled with gas "to carry at night, with which, and his little steam carriage running on the road, he used to astonish the people." Apparently unknown to Murdock, previous observations had been made as to the inflammability of gas from coal. Long before this Dr. Clayton described some observations on coal-gas, which he called "the spirit of coals." He filled bladders with this gas and kept them for some time. Upon his pricking one of them with a pin and applying a candle, the gas burned at the hole. Thus Clayton had a portable gas-light. He was led to experiment with distillation of coal from some experiences with gas from a natural coal bed, and he thus describes his initial laboratory experiment:

I got some coal, and distilled it in a retort in an open fire. At first there came over only phlegm, afterwards a black oil, and then likewise, a spirit arose which I could no ways condense; but it forced my lute and broke my glasses. Once when it had forced my lute, coming close thereto, in order to try to repair it, I observed that the spirit which issued out caught fire at the flame of the candle, and continued burning with violence as it issued out in a stream, which I blew out, and lighted again alternately several times.

He then turned his attention to saving some of the gas and hit upon the use of bladders. He was surprised at the amount of gas which was obtained from a small amount of coal; for, as he stated, "the spirit continued to rise for several hours, and filled the bladders almost as fast as a man could have blown them with his mouth; and yet the quantity of coals distilled was inconsiderable."

Although this account appeared in the Transactions of the Royal Society in 1739, there is strong evidence that Dr. Clayton had written it many years before, at least prior to 1691.

But before entering further into the early history of gas-lighting, it is interesting to inquire into the knowledge possessed in the seventeenth century pertaining to natural and artificial gas. Doubtless there are isolated instances throughout history of encounters with natural gas. Surely observant persons of bygone ages have noted a small flame emanating from the end of a stick whose other end was burning in a bonfire or in the fireplace. This is a gas-plant on a small scale; for the gas is formed at the burning end of the wooden stick and is conducted through its hollow center to the cold end, where it will burn if lighted. If a piece of paper be rolled into the form of a tube and inclined somewhat from a horizontal position, inflammable gas will emanate from the upper end if the lower end is burning. By applying a match near the upper end, we can ignite this jet of gas. However, it is certain that little was known of gas for illuminating purposes before the eighteenth century.

The literature of an ancient nation is often referred to as revealing the civilization of the period. Surely the scientific literature which deals with concrete facts is an exact indicator of the technical knowledge of a period! That little was known of natural gas and doubtless of artificial gas in the seventeenth century is shown by a brief report entitled "A Well and Earth in Lancashire taking Fire at a Candle," by Tho. Shirley in the Transactions of the Royal Society in 1667. Much of the quaint charm of the original is lost by inability to present the text in its original form, but it is reproduced as closely as practicable. The report was as follows:

About the latter End of Feb. 1659, returning from a Journey to my House in Wigan, I was entertained with the Relation of an odd Spring situated in one Mr. Hawkley's Ground (if I mistake not) about a Mile from the Town, in that Road which leads to Warrington and Chester: The People of this Town did confidently affirm, That the Water of this Spring did burn like Oil.

When we came to the said Spring (being 5 or 6 in Company together) and applied a lighted Candle to the Surface of the Water; there was 'tis true, a large Flame suddenly produced, which burnt the Foot of a Tree, growing on the Top of a neighbouring Bank, the Water of which Spring filled a Ditch that was there, and covered the Burning-place; I applied the lighted Candle to divers Parts of the Water contained in the said Ditch, and found, as I expected, that upon the Touch of the Candle and the Water the Flame was extinct.

Again, having taken up a Dish full of water at the flaming Place, and held the lighted Candle to it, it went out. Yet I observed that the Water, at the Burning-place, did boil, and heave, like Water in a Pot upon the Fire, tho' by putting my Hand into it, I could not perceive it so much as warm.

This Boiling I conceived to proceed from the Eruption of some bituminous or sulphureous Fumes; considering this Place was not above 30 or 40 Yards distant from the Mouth of a Coal-Pit there: And indeed Wigan, Ashton, and the whole Country, for many Miles compass, is underlaid with Coal. Then, applying my Hand to the Surface of the Burning-place of the Water, I found a strong Breath, as it were a Wind, to bear against my Hand.

When the Water was drained away, I applied the Candle to the Surface of the dry Earth, at the same Point where the Water burned before; the Fumes took fire, and burned very bright and vigorous. The Cone of the Flame ascended a Foot and a half from the Superficies of the Earth; and the Basis of it was of the Compass of a Man's Hat about the Brims. I then caused a Bucket full of Water to be pour'd on the Fire, by which it was presently quenched. I did not perceive the Flame to be discoloured like that of sulphurous Bodies, nor to have any manifest Scent with it. The Fumes, when they broke out of the Earth, and press'd against my Hand, were not, to my best Remembrance, at all hot.

Turning again to Dr. Clayton's experiments, we see that he pointed out striking and valuable properties of coal-gas but apparently gave no attention to its useful purposes. Furthermore, his account appears to have attracted no particular notice at the time of its publication in 1739. Dr. Richard Watson in 1767 described the results of experiments which he had been making with the products arising from the distillation of coal. In his process he permitted the gas to ascend through curved tubes, and he particularly noted "its great inflammability as well as elasticity." He also observed that "it retained the former property after it had passed through a great quantity of water." His published account dealt with a variety of facts and computations pertaining to the quantities of coke, tar, etc., produced from different kinds of coal and was a scientific work of value, but apparently the usefulness of the property of inflammability of coal-gas did not occur to him.

It is usually the habit of the scientific explorer of nature to return from excursions into her unfrequented recesses with new knowledge, to place it upon exhibition, and to return for more. The inventor passes by and sees applications for some of these scientific trophies which are productive of momentous consequences to mankind. Sir Humphrey Davy described his primitive arc-lamp three quarters of a century before Brush developed an arc-lamp for practical purposes. Maxwell and Hertz respectively predicted and produced electromagnetic waves long before Marconi applied this knowledge and developed "wireless" telegraphy. In a similar manner scientific accounts of the production and properties of coal-gas antedated by many years the initial applications made by Murdock to illuminating purposes.

Up to the beginning of the nineteenth century the civilized world had only a faint glimpse of the illuminating property of gas, but practicable gas-lighting was destined soon to be an epochal event in the progress of lighting. The dawn of modern science was coincident with the dawn of a luminous era.

At Soho foundry in 1798 Murdock constructed an apparatus which enabled him to exhibit his lighting-plan on a larger scale and to experiment on purifying and burning the gas so as to eliminate odor and smoke. Soho was an unique institution described as a place

to which men of genius were invited and resorted from every civilized country, to exercise and to display their talents. The perfection of the manufacturing arts was the great and constant aim of its liberal and enlightened proprietors, Messrs. Boulton and Watt; and whoever resided there was surrounded by a circle of scientific, ingenious, and skilful men, at all times ready to carry into effect the inventions of each other.

The Treaty of Amiens, which gave to England the peace she was sorely in need of, afforded Murdock an opportunity in 1802 favorable for making a public display of gas-lighting. The illumination of the Soho works on this occasion is described as "one of extraordinary splendour." The fronts of the extensive range of buildings were ornamented with a large number of devices which displayed the variety of forms of gas-lights. At that time this was a luminous spectacle of great novelty and the populace came from far and wide "to gaze at, and to admire, this wonderful display of the combined effects of science and art."