Stephen Gray (1666-1736) [Wikipedia] Conduction of Electricity through Materials
1729	Stephen Gray A letter to Cromwell Mortimer, M. D. Secr. R. S. containing several experiments concerning electricity by Mr. Stephen Gray Philosophical Transactions of the Royal Society of London, Volume 37, pp. 18-44 (1731). [DOI] [JSTOR] Note that the experiments were performed in 1729-1730.