Dalton wondered why the heavier and lighter gases in the atmosphere did not separate as oil and water do. He finally concluded that the constituent of gases must exist in the form of 21 particles or atoms and that these must be completely mixed together in the 22 . This threw a new light in the laws of definite proportions. It was 23 necessary to suppose that the atoms could combine into small groups of uniform 24 and so form more complex substance; 25 the mystery of this law was solved. Dalton suggested, for example, that carbon monoxide is formed by the one with one 26 of atoms of carbon and oxygen, 27 carbon dioxide results from a single 28 of carbon uniting with two atoms of oxygen. Assuming this to be true, then the definite proportions of Prouts's low 29 all chemical compounds the different constituents always enter in unvarying proportions would naturally unit the relative weights of the many 30 kinds of atoms.