The elements which are the most widely diffused have small atomic weights.

If all the elements are arranged in the order of their atomic weights, a periodic repetition of properties is obtained. This is expressed by the law of periodicity.

The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.

There exists everywhere a medium in things, determined by equilibrium.

No law of nature, however general, has been established all at once; its recognition has always been preceded by many presentiments.

Elements which are similar as regards their chemical properties have atomic weights which are either of nearly the same value (eg. Pt, Ir, Os) or which increase regularly (eg. K, Ru, Cs).

When the elements are arranged in vertical columns according to increasing atomic weight, so that the horizontal lines contain analogous elements again according to increasing atomic weight, an arrangement results from which several general conclusions may be drawn.