A new system of chemical philosophy
John Dalton(1766-1844)
 Dalton, Manchester’s brilliant scientist, and one of the pioneers of meteorology culminated his outstanding work in meteorology in 1793 before he turned to chemistry. He performed a series of lectures which were made for the purpose of complementing this work in 1799. In one of these lectures which was published later in 1805, he not only indicated the shift in his interest but also proposed a new theory of chemical combination. He developed this theory minutely and completed it systematically in this work.
 Dalton maintained that the molecules of a compound were a combination of the particles in elements and these particles could only be combined in a simple ratio of their weights. He concluded that all matter consisted of these particles which were indestructive, indivisible, ultimate, constructive materials. He named this particle ‘the atom’ according to Domoncritus’s theory of atomism. He first measured the weight of atoms in several elements on the basis of the weight of a hydrogen atom, considered to be the lightest atom, and thus was the first to fix the table of atomic weights. He also proposed a system of simple symbols to express atoms and their combinations, the first attempt to create a chemical symbol. Because Dalton’s symbol was pictographic and impractical, however, it was replaced shortly after that by Berzelius’s proposition, which provided a basis for the present system.
 Volume I and II of this work became a classic in the field of chemistry that ranked with Lavoisier’s “Traite Elementaire de Chemie”. Dalton’s atomism was subsequently developed by Berzelius, and later provided a firm foundation for modern physical chemistry.