THE STORY OF LIGHT

Auckland Star, Volume LXVII, Issue 235, 3 October 1936, Page 19 (Supplement)

THE STORY OF LIGHT

By E. HITCHCOCK (General Manager of the Christchurch Municipal Electricity Dept.)

IF you lived in London and could take a walk within quite a sliort distance of the Houses of Parliament you could still find among the

older residences some houses with queer, trumpet-shaped fittings by the front door. There was a time, really not very many years ago, when street lights were unknown, and people either carried torches or were guided home by footmen carrying a torch or lantern. This fitting by the door was used to "snuff," or quench, the torch when the people reached their homes. We forget sometimes that the wonderful lighting which we now have at night in our homes and in the streets of our towns has come only in recent years. It was not until the electric lamp was invented that man really completed his conquest of darkness. Long ages ago, when human beings dwelt in caves, the only light or warmth that they knew was that which came from the sun. When, each evenbig, those primitive people saw the sun setting in the west, they hurried to find refuge in a cave, because the darkness frightened them. There may have been many real reasons for their fears, but there were probably many imaginary ones as well. Their minds were childlike, and were filled with dread of the night. Perhaps it is some dim unconscious memory of those past ages which even now makes some nervous children quite needlessly afraid of the dark.

Tlion, the legend tells us, Prometheus the Titan stole the fire from heaven. Probably what actually happened was that someone discovered that fire could be struck from the rock or produced by the friction of sticks rubbed together. Thus primitive man was able to gather round the fire. It warjned him, and the light from the llamcs calmed his fears. Gradually man learned better ways of making light, but progress was very slow. As the centuries passed he discovered how to make the torch, the rush light and the tallow dip. Then came the candle, which was much better and brighter, but it flickered and burnt unevenly in a draught. It was, however, a great improvement 011 all previous kinds of lighting, and is still used to-day in places where there is no electricity. Shakespeare called it "the little candle which throws its beam so far." All children should read the "Chemical History of a Candle," which was written specially for children by the great English scientist Michael Faraday. After the candle came the kerosene lamp, which often smoked and cracked its glass if the wick was not kept properly trimmed. Gas lighting was another great advance, and served for many years. But man's real victory over darkness came with the invention of the electric lamp. It was only after many years of work, nnd many failures, that inventors and scientists showed that it was possible to make a lamp which could be lighted by electricity. Almost at the same time, in 1878, only 58 years ago, Sir Joseph

Swan in England and Thomas A. Edison, the great American inventor, were each successful in making an olectrie lamp. In the first lamps they made, the filament (the part that glows so brightly) was made of carbon. Now, carbon is familiar to most of us as soot, charcoal, or the graphite in pencils. The great difficulty these inventors had to overcome was how to make the carbon into fine threads which would not be easilv broken. Finally they succeeded.

The next process was to fix the fine threads of carbon into a glass bulb from which all the air had been extracted. If any air had been left in the bulb the filament would have been burnt by the electricity. When electricity was passed through it the carbon glowed brightly and became a source "of light. The carbon lamp was used for many years, but now it is used only for special purposes. Inventors discovered that a lamp having a metal filament gave a much more brilliant light, but it was only after many years of searching that a metal was discovered from which the filaments could be made. Modern lamps have, filaments made of tungsten, a valuable metal found chiefly in the tin mines of Cornwall and Australia. When separated from the tin it is a fine black powder. After it has been placed under very great pressure in a machine it becomes a hard metal. It is used because it can be drawn into fine wires of very great strength. When an electric current is passed through it, it becomes very hot, and glows with a brilliant white light, but it must be prevented from burning away by being in a vacuum or surrounded by a special gas. If you take in your hand an electric lamp bulb (it should rightly be called just a lamp) and look closely at it, you will see on the brass cap surrounding the smaller end two little pieces of solder. They are the terminals, or contacts, which connect the filament to the electric current. Wires made of special steel and plated with copper lead from these terminals through the glass at the small end of the lamp. These wires are embedded in the glass so that no air can pass into the bulb, and .they are joined to the tungsten wires. These tungsten wires are held in place by supporting wires, which in turn are held by a glass stem or rod. If, while the lamp is switched on. you look at it through a piece of smoked or dark coloured glass, you will notice how neatly and evenly the wires are separated, and what a beautiful and delicate piece of work it is. Practically all the work of making electric lamps is done by very costly and accurate machines. To make so strong and robust an article, which is at the same time both fragile and exact, is indeed a modern miracle. Electric lighting has become so familiar to us all that we forget how many years of work and study by scientists and inventors it has taken to make the wonderful and reliable lamp we have to-day, and, above all, to make it at a price which allows everyone to use it. The electric lamp which we buy for a shilling or two has cost in thoughg and labour and long searching what many hundreds of thousands of pounds could not pay for. For many years great men of science, engineers, inventors and chemists gave the best of their lives to win from Nature the secret of controlled light. Let us honour the memory of those who made the victory possible.