The subject‐matter of geophysical‐chemistry may be defined as “the physical properties and chemical reactions of the substances and aggregates that make up the earth”. It may therefore be roughly divided into two parts: A. Properties and reactions of materials accessible at the earth's surface. B. Properties and reactions of materials in the earth's interior.Each of these may again be sub‐divided as follows:1. Properties and reactions of individual chemical substances; for example, the silicate minerals.2. Properties and reactions of aggregates; for example, oceanic water, silicate rocks.3. Properties and reactions of larger units of matter; for example, glaciers, b