Drugs are now scientifically classified and prepared, the full resources of science being used in their manufacture. American chemists have invented machinery and methods of preparing new drugs. Citrate of magnesia was invented by Henry Blair, of Philadelphia. Many other valuable remedies came from his laboratory, including sirup of phosphates. CHAPTER XVI ELECTRICITY AND RADIOACTIVITIES Among the most marvelous scientific developments of the nineteenth century those in the electrical field claim universal attention. It was only as recently as 1844 that Morse introduced electric telegraphy. The telephone was introduced by Alexander Graham Bell in 1876 and Edison built one of his early dynamos in 1878 and in 1879 made his first high resistance incandescent lamp for parallel operation. The first Edison power and lighting station was opened at 257 Pearl Street, New York City, in 1882. Although electrical phenomena were understood in a general way thousands of years ago, they were not studied and applied to practical purposes until the sixteenth century when William Gilbert carried out his classical experiments in the reign of Queen Elizabeth. The Leyden jar was discovered in the early half of the eighteenth century. From experiments carried out with these jars a great number of important inventions were derived and our knowledge of electricity was for many years dependent upon researches of this kind. Benjamin Franklin in experimenting with the Leyden jar found that its electrical discharges were similar to those of lightning and he subsequently discovered that the inner part of the jar, when charged with a frictional current, was positively electrical while the outer portion was negative. The voltaic pile was invented in 1796 as a result of Galvani's experiments in physiological electricity and Sir Humphry Davy exhibited the first practical electrical lamp before the Royal Society in 1809. The dynamo was, in substance, invented by Faraday, and described by him before the Royal Society in 1831. This was, perhaps, the greatest of all electrical triumphs because it gave engineers a practical means of generating and using electrical currents of any desired dimensions. Bunsen in 1840 devised a means for making carbon rods for arc lamps, and Edison made practical carbon incandescent lamp filaments in 1879. Faraday's invention promoted all of these lighting discoveries. The engine-driven electric dynamo was made a practical machine in 1870 and thenceforward became the source of power of a great multitude of secondary machines, such as electric street cars, marine engines, power plants, and forging hammers.