Gay-Lussac's law of gaseous volumes is derived from $.......$.

Define the law of multiple proportions. Explain it with two examples. How does this law point to the existence of atoms?

Statement $1$: The mass ratio of hydrogen to oxygen in water obtained from rivers,wells,lakes,or seas is always $1:8$.
Statement $2$: In $1799$,the scientist Joseph Proust proposed the Law of Definite Proportions.

Define the Law of Multiple Proportions.

Two elements $X$ and $Y$ have atomic weights of $14$ and $16$. They form a series of compounds $A, B, C, D$ and $E$ in which for the same amount of element $X$,the amounts of $Y$ are present in the ratio $1 : 2 : 3 : 4 : 5$. If the compound $A$ has $28$ parts by weight of $X$ and $16$ parts by weight of $Y$,then the compound $C$ will have $28$ parts by weight of $X$ and:

One part of an element $A$ combines with two parts of another element $B$. Six parts of the element $C$ combine with four parts of the element $B$. If $A$ and $C$ combine together,the ratio of their weights will be governed by