With the recent progress of oceanography and the accumulation of data regarding the biological and chemical conditions of ocean water many oceanographers have become interested in correlations which relate to_ organic production ·and chemical cycles in the sea (Redfield, 1934; Seiwell, 1935; Harvey, et al, 1935; Fleming, 1940 ; Riley, 1941b). Since such studies require an accurate knowledge of conditions in the sea it is of prime importance to have some method for measuring the potential synthetic capacity of the sea which can be used in survey work as well as at fixed stations.