CHAPTER 4: Hard Spheres and Pictograms, The First Concrete Atomic Theory: John Dalton (Northern England and Manchester)

John Dalton started his scientific career as a meteorological observer and chronicler but soon expanded his interest to investigate the components of ordinary air. We describe his early life and education, his formulation of the Laws of Partial Pressures and Multiple Proportions, and his famous atomic theory (1808) that incorporated Lavoisier's Law of Conservation of Mass, Proust's Law of Definite Proportion and the Greek ideas of indivisible atoms. We discuss his colorblindness (“daltonism”), the symbols he invented to represent atoms and molecules (“pictographs”), his table of atomic weights, and how he used his own data and that gathered by his pneumatic predecessors Black, Davy, and Priestley to advance his ideas. Unfortunately, his adherence to a “rule of greatest simplicity” hindered the establishment of accurate tables of atomic weights for half a century. The many sites described include his birthplace in Eaglesfield, the Quaker Meeting House in Pardshaw Hall, the Stramongate School and the Quaker Tapestry House in Kendall, and the many sites in Manchester, including his statue and the Ford Madox Brown mural in the Manchester Town Hall, and the Dalton manuscripts available for viewing in the John Rylands Library.