a British chemist, is credited with discovering the flow of electricity in 1729. In the 1730s, Gray conducted experiments demonstrating that some materials can conduct the static charges of electricity (for example wet hemp) for distances as great as 765 feet while others (such as silk thread), did not conduct electricity at all. From these experiments, Gray showed that electrification is a surface effect and that electricity will move freely along some materials (conductors), which is a fundamental principle of the telegraph.