A temperature of 40.1 ° F., the carbonic acid amounts to 51 J5 cc. per litre, and the oxygen only to 2.19 cc. Vegetable plankton in sunlight can reverse this process, assimilating the carbon of the carbonic acid and restoring the oxygen to solution, as was proved by Martin Knudsen and Ostenfeld in the case of diatoms. Little is known as yet of the distribution of carbonic acid in the oceans, but the amount present seems to increase with the salinity as shown by the four observations quoted: Water from Gulf of Finland of 3.2 per mille salinity =17.2 cc. C02 Western Baltic of 14.2 North Atlantic of .0, , 49'0 Eastern Mediter ranean of 39.o, , =53'0, , Unfortunately the very numerous determinations of carbonic acid made by J.