In the first half of 1793, aged 26, Dalton took the position of teacher of mathematics and natural philosophy at Manchester’s New College, a dissenting college.
In 1794, he wrote his first scientific paper which he called: Extraordinary Facts Relating to the Vision of Colours.
This was the first ever paper to discuss color blindness. Dalton had realized the condition was hereditary, because he and other members of his family had it.
Ultimately, Dalton’s theory for color blindness was wrong, but as he was the first person ever to research it, the condition became known as Daltonism.
Further research papers followed, in the physical sciences: heat conduction, gas expansion by heat, the properties of light, the aurora borealis, and meteorology.
In 1800, Dalton began earning a living as a private tutor in science and mathematics. He resigned from New College, which was in financial difficulty.