[Sidenote: =The first great electrical exhibition=] In the winter of 1880, in Menlo Park, Edison gave to the public an exhibition of his electric light. Visitors came from all parts of the country to see this wonderful show. Seven hundred lights were put up in the streets, and inside the buildings. Edison had produced a much better light than any that had been used before. =202. A Great New Industry.= Edison also had a part in another invention for which Americans can claim most of the credit--moving pictures. [Sidenote: =Settling a racetrack dispute=] A dispute about horseracing did most for the discovery of moving pictures. The question was whether a horse ever had all four feet off the ground at once. To settle it, Edward Muybridge, an employee of the government, was called in. He stretched cords, fastened to the shutters of a row of cameras, across a racetrack. As the horse ran past, it took its own pictures. Later Muybridge made a camera which would take pictures very quickly, but he could not show his pictures well. [Sidenote: =Edison's camera=] Edison in 1892 invented a camera which used long strips of celluloid film. These pictures were looked at through a slot by one person at a time. Another government worker, C. Francis Jenkins, invented the first complete moving picture machine in 1894. [Sidenote: =The moving picture business=] At first people were slow to welcome the new kind of play. Now it is claimed that our fifth largest industry is moving pictures. Probably as many tickets are sold here each year as there are people in the world. [Sidenote: =Moving pictures of the war=] In the war each army had its own moving picture camera men. They took pictures of ships torpedoed, of airplane battles, and of the fighting among the icy peaks of the Alps, often at great danger to their own lives. Great events of world history like the signing of the armistice can now be recorded for future times. Such pictures teach us things that cannot easily be learned from books. Many schools have a machine of their own, and use moving pictures as a part of their regular class work. The subject is first outlined, then the pictures are shown, and afterwards the pupils write about what they have learned. [Sidenote: =Moving pictures in schools=] Some schools have films of their own. Others find it easy to get them. Our government sends out educational films on silo building, dairying, airplane manufacture, and many government activities. Business firms have films to loan on shoes, soap, automobiles, and other things they make. Regular film companies have pictures of animal life, the natural wonders of our country, current events, foreign countries, and other subjects suitable for school use, such as the teaching of cube root by moving picture cartoons.