But there is also a law of _multiple proportions_. It is found that when one element forms more than one compound with a second element, the quantities of the first element which combine with the combining weight of the second element are always simple multiples--never fractions--of the combining weight of the first element. We have seen that the _atomic_ weight of oxygen is 16--i.e., 16 times heavier than the lightest element, hydrogen, which is therefore (on the relative scale of atomic weights) 1. But the _combining_ weight of oxygen is 8--i.e., eight _parts_ of oxygen will combine with so many parts (combining weight) of some other element. Suppose we take for example nitrogen. Now the _combining_ weight of nitrogen is 14, and its _atomic_ weight is also 14. Fourteen parts of nitrogen will combine therefore with eight parts of oxygen. But fourteen parts of nitrogen will also combine with four simple multiples of eight parts of oxygen, forming in all five different compound substances. For example: 14 parts of nitrogen combine with 16 or 2x8 parts of oxygen. 14 parts of nitrogen combine with 24 or 3x8 parts of oxygen. 14 parts of nitrogen combine with 32 or 4x8 parts of oxygen. 14 parts of nitrogen combine with 40 or 5x8 parts of oxygen. John Dalton advanced a theory satisfactorily to explain why in successive compounds the amount of oxygen goes up in jumps, and why this jump in each case is equivalent to the combining weight of oxygen. The regular jumps in the case of the five nitrogen compounds simply mean that one more atom has entered, in each successive case, into combination. These combining weights, as we have seen, simply represent the relative weights of the various elements. “Atomic weight” is merely the name given by Dalton to the relative combining weights of the atoms. He had no information as to how many atoms actually combine in making a compound, much less of the actual weight of the single atoms of the elements. Nor did he know _why_ atoms combine at all, in any proportions, but, being a thorough-going Newtonian, both his physical theory and his chemical theory have a common basis in Newton’s doctrine of mutually repulsive atoms. If an element A unites with an element B, the repulsion of the atoms of B from one another must tend, he thought, to the formation of a binary compound. “Binary compounds must first be formed, then ternary, and so on, till the repulsion of the atoms of B refuses to admit any more.”[28] While we have traveled quite a distance in atomic and chemical theory since the days of John Dalton (1766-1844), it is to the everlasting credit of this (at the time) obscure and poverty-stricken teacher of mathematics and physics that he gave us, in 1808, “A new System of Chemical Philosophy” which unites the atomic theory of modern science, first advanced by his admirers and contemporaries, Baron J. J. Berzelius (1779-1848) and Sir Humphrey Davy (1778-1829).