That all elemental bodies consist of aggregations of atoms, not united fortuitously, but according to fixed proportions. The four laws of Dalton are—constant proportion, reciprocal proportion, multiple proportion, and compound proportion.
This has nothing to do with the atomic theory of Leucippus. It merely means that gases and other elements always combine in certain known ratios or units.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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