=Carbonic Acid and Climate.=--The great importance of the carbonic acid in the atmosphere as a factor in determining the climate of the earth has been confirmed by the researches of a considerable number of investigators. Its work appears to be that of an absorbent of the sun's radiant heat, retaining it and preventing its passing by us and leaving us in the cold temperature of space. Tyndall computes that it has in this capacity a power eighty times that of oxygen or nitrogen, while it is excelled by water vapor with ninety-two times that of those gases. Lecher and Pretner, on the other hand, believe that carbonic acid is the only agent concerned in the service. Mr. Cyrus F. Talman, Jr., in view of the fact that carbonic acid is an important factor among geological agencies, has published, in the Journal of Geology, a study of the conditions of the content of that gas in the ocean, a study that leads to the consideration of the chemistry of the ocean. It seems to be clear that with falling temperature the ocean will dissolve carbonic acid from the air. Dr. T. C. Chamberlin has shown that the amount of carbonic acid in the atmosphere at any one time, and therefore the climate of the earth at that time, depends upon the value of the ratio of the supply of the gas to its depletion. Besides the continuous supply that the atmosphere receives from the interior of the earth and from planetary space and the continuous depletion due to the formation of carbonates in place of the igneous alkali earth silicates, there are variations in the ratio of supply to depletion dependent upon the attitude of the land and the water. A large exposure of land surface is correlated with a rapid solution of calcium and magnesium carbonates, which, becoming bicarbonates, represent a loss of carbonic acid to the atmosphere. On the other hand, the formation of the normal carbonate by lime-secreting animals causes a direct liberation of the second equivalent of the bicarbonate. Therefore extensive oceans and abundant marine life are correlated with warm climate. After a somewhat more minute discussion of the action, Mr. Talman concludes that the ocean very greatly intensifies the secular variation of the earth's temperature, although acting as a moderating agent in the minor cycles.