From the outset the idea had had the utmost tangibility in the
mind of Dalton. He had all along represented the different atoms
by geometrical symbols--as a circle for oxygen, a circle
enclosing a dot for hydrogen, and the like--and had represented
compounds by placing these symbols of the elements in
juxtaposition. Berzelius proposed to improve upon this method by
substituting for the geometrical symbol the initial of the Latin
name of the element represented--O for oxygen, H for hydrogen,
and so on--a numerical coefficient to follow the letter as an
indication of the number of atoms present in any given compound.
This simple system soon gained general acceptance, and with
slight modifications it is still universally employed. Every
school-boy now is aware that H2O is the chemical way of
expressing the union of two atoms of hydrogen with one of oxygen
to form a molecule of water. But such a formula would have had
no meaning for the wisest chemist before the day of Berzelius.

The universal fame of the great Swedish authority served to give
general currency to his symbols and atomic weights, and the new
point of view thus developed led presently to two important
discoveries which removed the last lingering doubts as to the
validity of the atomic theory. In 1819 two French physicists,
Dulong and Petit, while experimenting with heat, discovered that
the specific heats of solids (that is to say, the amount of heat
required to raise the temperature of a given mass to a given
degree) vary inversely as their atomic weights. In the same year
Eilhard Mitscherlich, a German investigator, observed that
compounds having the same number of atoms to the molecule are
disposed to form the same angles of crystallization--a property