=201. Edison's Inventions.= In 1873 Edison established his first laboratory or workshop in Newark, New Jersey. Here he gathered more than three hundred men to turn out the inventions pertaining to electricity which his busy brain suggested. They were all as enthusiastic over the inventions as Edison himself. No fixed hours of labor in this shop! When the day's work was done the men often begged to be allowed to return to the shop to complete their work. [Sidenote: =More inventions=] [Sidenote: =Builds a new laboratory and gathers a fine library=] Many telegraph and telephone inventions were made in this laboratory. There were forty-five inventions all told. They brought in so much money that Edison decided they must have a better place to work. He built at Menlo Park, New Jersey, twenty-four miles from New York City, the finest laboratory then in the world. On instruments alone he spent $100,000. In the great laboratory at Menlo Park Edison gathered one of the finest scientific libraries that money could buy. This library was for the men in the factory--to help them in their inventions and to give them pleasure. [Sidenote: =Invents the microphone=] The microphone is one of Edison's inventions. Its purpose is to increase sound while sending it over the wire. The passing of a delicate camel's-hair brush is magnified so as to seem like the roar of a mighty wind in a forest of giant pines. [Illustration: THE PHONOGRAPH] [Sidenote: =The megaphone=] Next came the megaphone, an instrument to bring far-away sounds to one's hearing. By means of this instrument, persons talking a long distance apart are able to hear each other with ease. The phonograph, which can reproduce the human voice and other sounds almost perfectly, was invented by Edison in 1876. [Illustration: EDISON'S GREAT WORKSHOP AT ORANGE, NEW JERSEY] [Sidenote: =Edison's first phonograph=] Sounds reach the ear by means of air waves which the sounding body sets in motion. In Edison's first phonograph these waves struck a bit of taut parchment, and were marked by a needle on a tinfoil disc. But tinfoil does not hold its shape well. In 1888 Edison patented a better phonograph in which the record was made on a wax disc. Phonograph records are now made with one hundred grooves to an inch. Each groove is not more than four one-thousandths of an inch deep. A lever tipped with sapphire cuts the grooves. Its tiny marks have been photographed--one way of seeing a sound! [Sidenote: =What the phonograph does=] The phonograph is used everywhere for amusement. It preserves the voices of great singers for the future. With it songs and bits of folklore can be collected in languages that are now dying out. [Sidenote: =The electric light=] Edison has put into practical use many principles discovered by other men. He does not claim to be the discoverer of the electric light. He did much, however, to make it useful to people in lighting their houses, and also in lighting great cities.