The weights of oxygen which combine with 4.66 parts by weight of nitrogen to form the second and third compounds, respectively, must be whole multiples of 2.66; these weights are 5.32 and 10.64.Now 5.32 = 2.66 x 2, and 10.64 = 2.66 x 4.

Hence, the quantities by weight of oxygen which combine with one and the same weight of nitrogen are such that two of these quantities are whole multiples of the third quantity.
Dalton's application of the Greek atomic theory to the facts established by the analyses of compounds enabled him to attach to each element a number which he called the atomic weight of the element, and to summarise all the facts concerning the compositions of compounds in the statement, that the elements combine in the ratios of their atomic weights, or in the ratios of whole multiples of their atomic weights.
All the investigations which have been made into the compositions of compounds, since Dalton's time, have confirmed the generalisation which followed from Dalton's application of the atomic theory.
Even if the theory of atoms were abandoned, the generalisation would remain, as an accurate and exact statement of facts which hold good in every chemical change, that a number can be attached to each element, and the weights of the elements which combine are in the ratios of these numbers, or whole multiples of these numbers.
Since chemists realised the meaning of Dalton's book, published in 1808, and entitled, _A New System of Chemical Philosophy_, elements have been regarded as distinct and definite substances, which have not been divided into parts different from themselves, and unite with each other in definite quantities by weight which can be accurately expressed as whole multiples of certain fixed quantities; and compounds have been regarded as distinct and definite substances which are formed by the union of, and can be separated into, quantities of various elements which are expressible by certain fixed numbers or whole multiples thereof.

These descriptions of elements and compounds are expressions of actual facts.

They enable chemists to state the compositions of all the compounds which are, or can be, formed by the union of any elements.

For example, let A, B, C, and D represent four elements, and also certain definite weights of these elements, then the compositions of all the compounds which can be formed by the union of these elements are expressed by the scheme A_{_n_} B_{_m_} C_{_p_} D_{_q_}, where _m_ _n_ _p_ and _q_ are whole numbers.
These descriptions of elements and compounds also enable chemists to form a clear picture to themselves of any chemical change.