Franklin's electrostatic machine

[3] In 1745, German cleric Ewald Georg von Kleist and Dutch scientist Pieter van Musschenbroek discovered independently that the electric charge from these machines could be stored in a Leyden jar, named after the city of Leiden in the Netherlands.[3] In 1745, Peter Collinson, a businessman from London who corresponded with American and European scientists, donated a German "glass tube"[4] along with instructions how to make static electricity, to Franklin's Library Company of Philadelphia.[6][7][8] Franklin wrote a letter to Collinson on March 28, 1747,[9] thanking him, and saying the tube and instructions had motivated several colleagues and him to begin serious experiments with electricity.The machine was unique improvement over others made in Europe at the time, as the glass globe could be spun faster with much less labor.[24][25] The electricity produced by the machine, in the form of sparks, passed through a set of metal needles positioned close to the spinning globe.Franklin called this device an "electrical battery",[4] but that term later came to have a different meaning, referring instead to a set of one or more galvanic cells.Through his research, Franklin was among first to prove the electrical principal of conservation of charge in 1747:[16][24] a similar discovery was made independently in 1746 by William Watson.[42] He wrote Collinson and Cadwallader Colden letters about this theory,[43] and he described the kite experiment in the October 19, 1752 issue of the Pennsylvania Gazette.[49][50]) To test his theory, Franklin proposed a potentially deadly experiment, to be performed during an electrical storm, where a person would stand on an insulated stool inside a sentry box, and hold out a long, pointed iron rod to attract a lightning bolt.[15] A similar but less dangerous version of this experiment was first performed successfully in France On May 10, 1752, and later repeated several more times throughout Europe, though after a fatality in 1753 it was less frequently tried.[51] Franklin's friend Kinnersley traveled throughout the eastern United States in the 1750s demonstrating man-made "lightning" on model thunder houses to show a how an iron rod placed into the ground would protect a wooden structure.[13] Between 1747 and 1750, Franklin sent many letters to his friend Collinson in London about his experiments with the electrostatic machine and the Leyden jar, including his observations and theories on the principles of electricity.