Page:Popular Science Monthly Volume 56.djvu/637

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the composition, and on top of all came the Normans. These elements, none of which were extremely discordant with the others, became thoroughly mixed in the course of time, and matured into the English people as it is. The English resemble the Romans in their methods of colonization, political tact, practical sense, persistence, religious tolerance, the magnitude of their works and the boldness of their undertakings, and in their egotism working together with the principle of social solidarity. Both readily established themselves in new colonies, carrying there the civilization of the mother country and their systems of administration. The great roads and wonderful bridges constructed by the Romans are paralleled by the great Anglo-Saxon railway systems. As the Latin language became almost universal, so the English language is diffusing itself everywhere. But Signor Sergi fails to show why, if the English have taken so much from the Romans, the Italians, their direct descendants, have lost so much of what they once had. He reserves that question, after raising it, for future consideration.


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.


Pearl Mussels.—In his report to the United States Fish Commission on the Pearly Fresh-Water Mussels of the United States, Mr. Charles T. Simpson speaks of the great variety of conditions under which they live. They show great capacity for adaptation. Most of them are found in shallow water, but certain forms live at considerable depths. Some bury themselves among the fibrous roots of trees, some in the muddy, sandy banks just below the surface of the water, and some, as in Lake Tiberias (Palestine) and Lake Tanganyika (Africa), under six hundred or more feet of water. Ordinarily they die in a very short time if taken out of the water—in from twenty-four to forty-eight hours, as a rule—and they generally die in a few hours when exposed to the sun. But many species, thus tender in the open air, will lie buried in dried mud for a long time. In June, 1850, a living pond mussel was sent to London, from Australia, which had been out of water for more than a year. Along a small stream near Braidentown,