d their interactions.
Over the years, the exact process by which Dalton devised his atomic theory has been a topic of much debate. His own recollections are confusing; similarly, there is little consensus among the reported accounts of friends. There are several potential routes of development, and each has both reasonable documentation and disparities (4:106).
Dalton's "atom" was very similar to the "particle" described by Sir Isaac Newton in his Opticks. Newton's influence on Dalton is emphasized by the fact that many of his passages were copied into Dalton's notebooks. One such passage described atoms as indivisible homogenous particles. It reads as follows: ". . . God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles . . . so hard as never to wear or break in pieces (4:106-121)." In yet another passage, Newton describes the nature of these particles: "God is able to create particles of matter of several sizes and figures, and in several proportions to the space they occupy, and perhaps of different densities and forces . . . (4:106-121)." This Newtonian heritage predisposed Dalton to particulate concepts. Such a background, combined with studies of aeriform fluids, eventually led the scientist to formulate his own atomic theory.
In 1793, Dalton proposed that atmospheric air is comprised of a mixture of gases. Ten years later--after a series of experimental and theoretical investigations--Dalton concluded that these gases consist of atoms (6:30-31). In a lecture given by Dalton in 1835, he admitted the following: ". . . Nitrous oxide is composed of two particles of azote and one of oxygen. This was one of my earliest atoms. I determined it in 1803, after long and patient consideration and reasoning (4:103-104)." Additionally, on October 21, 1803, Dalton read the paper, "Theory of the Absorption of Gases by Water," to the Manchester Literary and Philosophical Society. ...