Stories of Useful Inventions. Forman Samuel Eagle
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Название: Stories of Useful Inventions
Автор: Forman Samuel Eagle
Издательство: Public Domain
Жанр: Зарубежная классика
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THE LAMP
Next to its usefulness for heating and cooking, the greatest use of fire is to furnish light to drive away darkness. Man is not content, like birds and brutes, to go to sleep at the setting of the sun. He takes a part of the night-time and uses it for work or for travel or for social pleasures, or for the improvement of his mind, and in this way adds several years to life. He could not do this if he were compelled to grope in darkness. When the great source of daylight disappears he must make light for himself, for the sources of night-light – the moon and stars and aurora borealis and lightning – are not sufficient to satisfy his wants. In this chapter we shall follow man in his efforts to conquer darkness, and we shall have the story of the lamp.
FIG. 1. – A FIREFLY LAMP.
We may begin the story with an odd but interesting kind of lamp. The firefly or lightning-bug which we see so often in the summer nights was in the earliest time brought into service and made to shed its light for man. Fireflies were imprisoned in a rude box – in the shell of a cocoanut, perhaps, or in a gourd – and the light of their bodies was allowed to shoot out through the numerous holes made in the box. We must not despise the light given out by these tiny creatures. "In the mountains of Tijuca," says a traveler, "I have read the finest print by the light of one of these natural lamps (fireflies) placed under a common glass tumbler (Fig. 1), and with distinctness I could tell the hour of the night and discern the very small figures which marked the seconds of a little Swiss watch."
FIG. 2. – A BURNING STICK WAS THE FIRST LAMP.
Although fireflies have been used here and there by primitive folk, they could hardly have been the first lamp. Man's battle with darkness really began with the torch, which was lighted at the fire in the cave or in the wigwam and kept burning for purposes of illumination. A burning stick was the first lamp (Fig. 2). The first improvement in the torch was made when slivers or splinters of resinous or oily wood were tied together and burned. We may regard this as a lamp which is all wick. This invention resulted in a fuller and clearer light, and one that would burn longer than the single stick. A further improvement came when a long piece of wax or fatty substance was wrapped about with leaves. This was something like a candle, only the wick (the leaves) was outside, and the oily substance which fed the wick was in the center.
FIG. 3. – THE CANDLE.
In the course of time it was discovered that it was better to smear the grease on the outside of the stick, or on the outside of whatever was to be burned; that is, that it was better to have the wick inside. Torches were then made of rope coated with resin or fat, or of sticks or splinters smeared with grease; here the stick resembled the wick of the candle as we know it to-day, and the coating of fat corresponded to the tallow or paraffin. Rude candles made of oiled rope or of sticks smeared with fat were invented in primitive times, and they continued to be used for thousands of years after men were civilized. In the dark ages – and they were dark in more senses than one – torch-makers began to wrap the central stick first with flax or hemp and then place around this a thick layer of fat. This torch gave a very good light, but about the time of Alfred the Great (900 A.D.) another step was taken: the central stick was left out altogether, and the thick layer of fat or wax was placed directly around the wick of twisted cotton. All that was left of the original torch – the stick of wood – was gone. The torch had developed into the candle (Fig. 3). The candles of to-day are made of better material than those of the olden time, and they are much cheaper; yet in principle they do not differ from the candles of a thousand years ago.
FIG. 4. – A SHELL FILLED WITH OIL AND USED AS A LAMP.
I have given the development of the candle first because its forerunner, the torch, was first used for lighting. But it must not be forgotten that along with the torch there was used, almost from the beginning, another kind of lamp. Almost as soon as men discovered that the melted fat of animals would burn easily – and that was certainly very long ago – they invented in a rude form the lamp from which the lamp of to-day has been evolved. The cavity of a shell (Fig. 4) or of a stone, or of the skull of an animal, was filled with melted fat or oil, and a wick of flax or other fibrous material was laid upon the edge of the vessel. The oil or grease passed up the wick by capillary action,6 and when the end of the wick was lighted it continued to burn as long as there were both oil and wick. This was the earliest lamp. As man became more civilized, instead of a hollow stone or a skull, an earthen saucer or bowl was used. Around the edge of the bowl a gutter or spout was made for holding the wick. In the lamp of the ancient Greeks and Romans the reservoir which held the oil was closed, although in the center there was a hole through which the oil might be poured. Sometimes one of these lamps would have several spouts or nozzles. The more wicks a lamp had, of course, the more light it would give. There is in the museum at Cortona, in Italy, an ancient lamp which has sixteen nozzles. This interesting relic (Fig. 5) was used in a pagan temple in Etruria more than twenty-five hundred years ago.
FIG. 5. – AN ETRUSCAN LAMP 2500 YEARS OLD.
FIG. 6. – AN ANCIENT LAMP.
Lamps such as have just been described were used among the civilized peoples of the ancient world, and continued to be used through the Middle Ages far into modern times. They were sometimes very costly and beautiful (Fig. 6), but they never gave a good light. They sent out an unpleasant odor, and they were so smoky that they covered the walls and furniture with soot. The candle was in every way better than the ancient lamp, and after the invention of wax tapers – candles made of wax – in the thirteenth century, lamps were no longer used by those who could afford to buy tapers. For ordinary purposes and ordinary people, however, the lamp continued to do service, but it was not improved. The eighteenth century had nearly passed, and the lamp was still the unsatisfactory, disagreeable thing it had always been.
FIG. 7. – AN ARGAND LAMP.
Late in the eighteenth century the improvement came. In 1783 a man named Argand, a Swiss physician residing in London, invented a lamp that was far better than any that had ever been made before. What did Argand do for the lamp? Examine an ordinary lamp in which coal-oil is burned. The chimney protects the flame from sudden gusts of wind and also creates a draft of air,7 just as the fire-chimney creates a draft. Argand's lamp (Fig. 7) was the first to have a chimney. Look below the chimney and you will see open passages through which air may pass upward and find its way to the wick. Notice further that as this draft of air passes upward it is so directed that, when the lamp is burning, an extra quantity of air plays directly upon the wick. Before Argand, the wick received no supply of air. Now notice – and this is very important – that the wick of our modern lamp is flat or circular, but thin. The air in abundance plays upon both sides of the thin wick, and burns it without making smoke. Smoke is simply half-burned particles (soot) of a burning substance. The particles pass off half-burned because enough air has not been supplied. Now Argand, by making the wick thin and by causing plenty of air to rush into the flame, caused all the wick to be burned and thereby caused it to burn with a white flame.
After the invention of Argand, the art of lamp-making improved by leaps and by bounds. More progress was made in twenty years after 1783 than had been made in twenty centuries before. New burners were invented, new and better oils were used, and СКАЧАТЬ
Hold the end of a dry towel in a basin of water and watch the water rise in the towel. It rises by capillary action.
Light a short piece of candle and place it in a tumbler, and cover the top of the tumbler. The experiment teaches that a flame must have a constant supply of fresh air and will go out if the air is shut off.