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Another classical example of theory rejection is the rejection of the phlogiston theory of combustion in the eighteenth century. The theory was introduced by George Stahl (1660-1734) to explain the process of the calcination used to prepare metals from their ores. Flammable substances such as wood were said to be rich in phlogiston, which was released by combustion. Metals were thought to be compounds of the metal`s calx and phlogiston. Metals were prepared from their calx by placing them in burning wood charcoal, which was thought to result in the transfer of phlogiston from the burning charcoal to the calx. The theory was further developed by Henry Cavendish (1731-1810) and Joseph Priestley (1733-1804). The Chemical Revolution brought greater attention to precise measurement of chemical processes, and it was found that the metal calx weighed more than the metal end product. While this led some to posit that phlogiston had negative weight, Antoine Lavoisier (1743-1794) posited supposed instead that a substance he called `oxygen` was released from the calx (which is now known as the metal`s oxide) during the formation of the metal. The phlogiston theory was rejected when the oxygen theory of combustion was accepted into the mosaic. [[CiteRef::Weisberg, Needham, and Hendry (2010)]]