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).

We must expect the discovery of many as yet unknown elements-for example, elements analogous to aluminum and silicon- whose atomic weight would be between 65 and 75.

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.

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

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.

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