1. The Law of Conservation of Mass
This law states that matter is neither created nor destroyed.
2. The Law of Definite Proportions
This law states that compounds contain the same proportions of elements.
For instance, carbon dioxide is 2.6 parts oxygen to 1 part carbon, by mass.
From these laws, Dalton concluded that elements must exist in discrete atoms.
This marked the first experimental support of the Greek theory.