John Dalton, in an engraving after an 1814 painting by William Allen. Note the charts with Dalton's atomic symbols lying on the table. Fisher Collection, CHF. John Dalton (1766–1844) John Dalton was an unassuming Quaker school teacher who worked in Manchester, England, for most of his career. The son of a shoemaker, he was the first meteorologist and studied color blindness as well. He is best known for creating our modern concept of atoms. Once Antoine-Laurent Lavoisier had revolutionized chemistry, the stage was set for Dalton to provide the theory that has underlain practical chemistry for nearly 200 years. Drawing on Lavoisier’s observation that matter is never created or destroyed in chemical reactions, and Joseph-Louis Proust’s observation that compounds always contain the same ratios of their component elements, Dalton thought the only reasonable conclusion was that matter was made of small indivisible particles, called atoms. Elements were made of identical atoms, while compounds were made of different kinds of atoms joined together to form tiny assemblies that would later be called molecules. Furthermore, each molecule in a compound was made of the same kinds of atoms and the same numbers of each kind. A chemical reaction was thus a rearrangement of the atoms that made up the molecules of reacting substances. Dalton’s theory united atomism with the idea of elements; atoms and molecules are microscopic explanations of the macroscopic phenomena of elements and compounds. Incidentally, his theory officially closed the book on alchemy. Since each element was made of a different kind of atom, and atoms were immutable in Dalton’s system, there was now a theoretical basis for rejecting the possibility of transmuting the element lead into the element gold.