When gas was first used, there was much opposition to it, as there usually has been to improvements in general. The citizens of Philadelphia protested for more than twenty years against the introduction of gas into that city for purposes of illumination. Some of the newspapers of the time called gas a "folly and a nuisance"; and one of the professors in the University of Pennsylvania declared that even if gas were the good thing its supporters were declaring it to be, tallow candles and oil lamps were good enough for him. But gas triumphed, and to-day the world could scarcely do without it, either for illumination or for fuel. The electric light had its beginning about 1800 in the experiments of Sir Humphry Davy, a British investigator. He discovered that if two pieces of carbon are brought into contact, completing a circuit through which an electric current flows, and if the carbon points are separated by a short distance, the points will become intensely hot and emit a brilliant light. The word _arc_, used in connection with the arc lamp or light, refers to the gap or arc between the two carbon points, across which the electric current leaps in creating the light. Following Sir Humphry Davy's experiments, several arc lights were invented, with greater or less degree of success, and about 1860 electricity was tried successfully for lighting in some lighthouses along the British coast. The widespread usage and the usefulness of the arc electric light, however, are due to Charles Francis Brush, an electrical inventor of Cleveland, Ohio, who in 1876 simplified the arc light so as to bring it into general use for lighting streets, large rooms, halls, and outdoor spaces. Brush was also the inventor of an electric-dynamo machine that has added to his fame. After the invention of the arc light, he took out more than fifty other patents. The incandescent electric light, for lighting residences and small rooms, came a little later as the invention of Edison. Thomas Alva Edison is one of the most remarkable men of all times and places. Alexander, Caesar, and Napoleon together did not benefit mankind as has this quiet American inventor. He was born at Milan, Ohio, February 11, 1847. His father was of Dutch descent and his mother was Scotch. The mother, who had been a teacher, gave him all the schooling he received. Early in life he showed great mental vigor and ingenuity. When he was twelve years old, he is said to have read the histories of Hume and Gibbon. [Illustration: THOMAS A. EDISON]