sunset the day is ending and the heavy darkness falls upon the land this darkness that long for man has learned to make its own daylight and our time man made daylight at hand but the touch of switch this was not always so when men began his kind quest of the dark he had only fire fire which he stayed while increasing the light thousands of years ago when man lived in caves fire was his most precious possession fire kept him warm protected him against wild beast and helped him a shade stone then the stairs for hunting in following years man took his f learned that he could increase their lives by burning single sticks called candle light this was his first attempt to use fire part light alone by the middle ages man had developed several different ways of lighting the indoors having discovered that wood with much pitch burned with a brighter flame and then what with only a little he soon began dipping his sticks into balls of picked he found also that melted teeth that vegetable but burning oil causes smoke when the fuel is consumed too rapidly to get rid of the smoke people frequently used another kind of lighting one that said only a little or a lot of time there's a flame this was accomplished by the way we don't know who cover the use of the way perhaps many men found for ages man i conceive the process of taking these tiny strands putting one end in a ball of oil and lighting the other this sort of well for the wake acted as a sort of block in which the oil on melted fat rose a little at a time until it reached a flame special weight were made with dozens of little threads braided together this made the fuel burn more slowly and give off a much cleaner and brighter light the principle of the work was employed in designing early lamps like this one which resembles a teapot the way it was led through a little spout so it could be pulled out easily as it burned down but the pod lands for cumbersome and hard to carry around and oil was not easy for all people to get better ideas for using weights were developed probably the simplest of these was awake laden some melted fat and allowed to dry when the weight was lifted simple handle a better candle could be made by dipping the wake into a bowl of melted fat holding it in the air until the fan had sat and dipping it again and again these candles called dips were much better than the earlier candle light the candle increased the light of the fire and reduced its heat thus by the end of the middle ages man had found these several ways of lighting the inside of his home but even as late as the seventeenth century the streets were still dark from sunset until dawn lanterns usually with candles inside were used for walking at night the middle of the eighteenth century cities were beginning to light the streets at night paris was the first city to install street lighting and london the second the lights weren't very good but they were better than none at all and so man had begun to create artificial daylight both indoors and out but he could do no more toward increasing the light and decreasing the heat of fire until the learn the nature of burning or combustion in a candle smelt sun forms a little puddle around the way through the way the melted wax rises to the flame the hot wax turns into colorless gas which collects around the way outside the gas packet combustion takes place when this gas which consists of carbon and hydrogen combines with the oxygen in the air much of the carbon however does not combine with the oxygen it once brought out a part of the flame it is heated sufficiently to glow it is these glowing bits of carbon give the light from the candle but when there are too many bits of carbon some of them do not become hot enough to glow these actually do in the light one of the first lighting improvements that came from a better knowledge of combustion was this lamp for the tube like wick and glass ten that these improvements allow the air to get to the middle of the wake so that all the carbon particles would be heated enough to glow is called an argon burner after it's within better who found this means of making indoor light brighter and cooler another form of gas land these lands use a new kind of fuel cal made around one hundred fifty years ago they were designed to permit the right quantity of air to mix with the gas but still as in the most primitive days man was using fire to create li the middle of the nineteenth century saw the beginning of a new era in the creation of man made daylight when a piece of iron is heated pot foraging turned first red and then the white hot giving off intense heat and light when this principle is applied to arc welding the light is so brilliant that the welder must take care to shield his eyes working from this idea of life man turn sticks of coal and later hard carbon into a brilliant car arc the principle of these five hundred carbon sticks was used by thomas edison when he fashioned the incandescent electric light over sixty years ago instead of carbon sticks edison used the filament charred cotton thread when he discovered glow man had taken his greatest strides toward turning my in today here i was light without fire sealed in a vacuum by a little filament gave off more light with less heat than any source man had yet found these incandescent light bulbs were rapidly improved so that they diffused allied softening it and spreading it met th obtained an excellent controllable source of light but he did not stop there he added a knowledge of how light is reflected light from any source travels are going in straight lines in every direction each position about the the same path this is one way man directs and brightened his light last we can control our light and lamp headlights and indirect lighting applying this knowledge of reflection to his incandescent light bulbs man has been able to add interest as well as better lighting to his offices and homes but still the incandescent electric light gives our much more heat than it does light so our way is been found to create more allied with reduced heat from glass tubes content with chemicals are filled with gases which light up when electrically charged these right sources f neon are different from any others because they are not the result of heating and our cities and we are still where increasing knowledge and ingenuity to