John Dalton was born September 6, 1766, in Eaglesfield, Cumberland, England and died July 27, 1844, in Manchester. A chemist and physicist, he developed the atomic theory of matter and hence is known as one of the fathers of modern physical science. Dalton, a teacher at the age of 12, spent most of his life in Manchester. He began his studies of meteorology in 1787. He made valuable observations concerning the Aurora Borealis, the trade winds, and the cause of rain. He determined the point of the maximum density of water and published the results of work on color blindness. In chemistry, his major work began around 1800. Dalton developed the law known as Dalton's Law of partial pressures. Dalton's Law states that the total pressure of gas is equal to the sum of the partial pressures of the individual component gasses. The partial pressure is the pressure that each gas would exert if it, alone, occupied the volume of the mixture at the same temperature. This empirical relation was stated in 1801. It follows from the kinetic theory of gasses under the assumption of a perfect (ideal) gas, and assumes no chemical interaction between the component gasses. It is approximately valid for real gasses at sufficiently low pressures and high temperatures.

He also found that gasses expand as their temperature is raised. Further experiments showed the solubility of gasses in water, the rate of diffusion of gases, and the constancy of composition of the atmosphere. Dalton determined the relative weights of atoms, developed the laws of definite and multiple proportions, and finally formulated the atomic theory which states that all elements are composed of tiny, identical, and indestructible particles. Many of these findings were included in his New System of Chemical Philosophy.