How did John Dalton describe the composition of Earth's atmosphere?

John Dalton, a pioneering English meteorologist and chemist, held the view that the atmosphere was a physical mixture of gases rather than a specific chemical compound.1

Specifically, he described the air as being composed of approximately 80 percent nitrogen and 20 percent oxygen. His understanding of the atmosphere was deeply connected to his work on partial pressure, which posits that each constituent gas in a mixture exerts the same pressure it would if it were the only gas present.1