Dalton Writing

Dalton, an English schoolteacher and amateur meteorologist, noticed how water could magically disappear into the air (evaporation) and later reappear as clouds and rain.  He reasoned that this could only happen if air was made up of tiny individual particles (atoms) with lots of empty space between them.  Dalton thought that not just air, but all matter, was made of atoms.

To him atoms were solid, indestructible spheres with no internal structure and atoms of different substances had different masses.  These atoms combined in simple, whole number ratios to make everything around us.

Of all the substances he looked at, hydrogen was the lightest so he gave hydrogen atoms a mass of 1, the smallest integer.  He found weights of other substances in relation to hydrogen, e.g. oxygen was 8X heavier than hydrogen so it was given a mass of 8.