A lecture at the Charterhouse, London on Stephen Gray's discoveries in electricity. In the early eighteenth century, Gray demonstrated that charges of electricity could be conducted by some materials for distances as great as 765 feet, while others did not conduct electricity at all. Eventually, he was able to send charges through 88 metres of wire suspended on silken threads to operate an electroscope - an instrument used to detect static electricity. By sending an electrical signal from one place to another, Gray established the basic principle of the electric telegraph.