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instance, a-b and b-a are but two permutaCombina. tion. tions of a and b. Similarly Combination is
their arrangement in groups without reference to the order of sequence; as for example, "a-b-c' is a combination involving a, b, and c, and 'b-a-c' is but another combination, both consisting simply of a, b, and c, grouped together. In Combination, it is worthy of note, we take notice only of the presence or absence of a certain thing and pay no regard to its place in order of time and space. There being but a. b, c, d and so on, it finds out only how many combinations could there possibly arise by taking at a time the two, three, or four of the symbols.
While investigating into the structure Application and composition of chemical things we subof Permuta; stitute, -H, N, O, C as symbolic representcombination.
ation of Hydrozen, Nitrogen, Oxygen and Carbon, the ultimate ruờiments or atoms of which are innumerable in number, in the places of a, b, c, d. Now experiment shows that it is due to the innumerable variety of atomic combinations of H, N, O and C.; that we have differences between the different
of the laws
tion and
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