NO. 2 HISTORY OF ELECTRIC LIGHT — SCHROEDER 3 



which Gilbert had discovered, would become electrified if rubbed. 

 Those substances which Gilbert could not electrify were conductors 

 of electricity. 



THE LEYDEN JAR 



The thought came to Von Kleist, Bishop of Pomerania, Germany, 

 about 1745, that electricity could be stored. The frictional machines 

 generated so small an amount of electricity (though, as is now known, 

 at a very high pressure — several thousand volts) that he thought he 

 could increase the quantity by storing it. Knowing that glass was 

 an insulator and water a conductor, he filled a glass bottle partly full 

 of water with a nail in the cork to connect the machine with the 

 water. Holding the bottle in one hand and turning the machine with 

 the other for a few minutes, he then disconnected the bottle from the 

 machine. When he touched the nail with his other hand he received 

 a shock which nearly stunned him. This was called the Leyden jar, 

 the forerunner of the present condenser. It received its name from 

 the fact that its discovery was also made a short time after by experi- 

 menters in the University of Leyden. Further experiments showed 

 that the hand holding the bottle was as essential as the water inside, 

 so these were substituted by tin foil coatings inside and outside the 

 bottle. 



Benjamin Franklin, American statesman, scientist and printer, made 

 numerous experiments with the Leyden jar. He connected several 

 jars in parallel, as he called it, which gave a discharge strong enough 

 to kill a turkey. He also connected the jars in series, or " in cascade " 

 as he called it, thus establishing the principle of parallel and series 

 connections. Noticing the similarity between the electric spark and 

 lightning, Franklin in 1752, performed his famous kite experiment. 

 Flying a kite in a thunderstorm, he drew electricity from the clouds 

 to charge Leyden jars, which were later discharged, proving that 

 lightning and electricity were the same. This led him to invent the 

 lightning rod. 



ELECTRICITY GENERATED BY CHEMICAL MEANS 



Luigi Galvani was an Italian scientist. About 1785, so the story 

 goes, his wife was in delicate health, and some frog legs were being 

 skinned to make her a nourishing soup. An assistant holding the legs 

 with a metal clamp and cutting the skin with a scalpel, happened to 

 let the clamp and scalpel touch each other. To his amazement the 

 frog legs twitched. Galvani repeated the experiment many times 



