Abstract
Realizing the importance of a quantitative method for identifying air masses, Prof. C. G. ROSSBY presented the consistent definitions of the equivalent-potential temperature and equivalent temperature, and developed the diagram which bears him name(1). It should be mentioned here that the wet-bulb-potential temperature and wet-bulb temperature can equally be used for the purposes of identification(2). So far as I know there is no unified presentation of simple, analytic definitions of these temperatures at present, so that it might be pointed out that the task of writing such a treatise is no mean one.
