[Illustration: FIG. 5.--AN ETRUSCAN LAMP 2500 YEARS OLD.] [Illustration: 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. [Illustration: 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 better wicks made. But all the new kinds of lamps were patterned after the Argand. The lamp you use at home may not be a real Argand, but it is doubtless made according to the principles of the lamp invented by the Swiss physician in 1783.