Page:Popular Science Monthly Volume 15.djvu/292

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THE POPULAR SCIENCE MONTHLY.

POPULAR MISCELLANY.

The National Academy of Sciences.—Professor O. C. Marsh, who, after the death of Professor Joseph Henry, became acting President of the National Academy of Sciences, in his address at the annual meeting of that body, held in Washington, April 15th, presented a detailed statement of the action of the Academy with regard to the reorganization of the survey of the Territories. He also submitted a report of the progress which has been made in putting into execution Professor Newcomb's plan for determining the distance of the sun by measuring the velocity of light. Professor Marsh justly congratulates the Academy upon the unanimity with which the members adopted the scheme for reorganizing the surveys, and on its embodiment without change in a law of Congress. The Academy, in all its deliberations upon this important matter, was strictly unpartisan, and acted without respect of persons. Whether the scheme which now goes into execution will lead to better results than the old plan of many independent surveys, Professor Marsh leaves to the historian to decide. For the purpose of carrying out Professor Newcomb's plan of determining the sun's distance, the sum of five thousand dollars has been appropriated by Congress; and the work of constructing the necessary apparatus will be commenced as soon as the appropriation is available. It is hoped by those who proposed this plan that the experiments will lead to a more accurate determination of the distance of the sun than can be reached by any other method known to astronomers.

 

The Growth of a Continent.—The history of the growth of the European Continent, as recounted by Professor Geikie, gives an instructive illustration of the relations of geology to geography. The earliest European land, he says, appears to have existed in the north and northwest, comprising Scandinavia, Finland, and the northwest of the British area, and to have extended thence through boreal and arctic latitudes into North America. Of the height and mass of this primeval land some idea maybe formed by considering the enormous bulk of the material derived from its disintegration. In the Silurian formations of the British Islands alone there is a mass of rock, worn from the land, which would form a mountain chain extending from Marseilles to the North Cape (1,800 miles), with a mean breadth of over thirty-three miles and an average height of 16,000 feet. The Silurian sea which spread across most of central Europe into Asia suffered great disturbance in some regions toward the close of the Silurian period. It was ridged up into land inclosing vast inland basins, the areas of some of which are still traceable across the British Islands to Scandinavia and the west of Russia. An interesting series of geographical changes can be traced, during which the lakes of the Old Red Sandstone were effaced, the sea that gradually overspread most of Europe was finally silted up, and the lagoons and marshes came to be densely crowded with the vegetation to which we owe our coal-seams. Later terrestrial movements led to the formation of a series of bitter lakes across the heart of Europe, like those now existing in the southeast of Russia. Successive depressions and elevations brought the open sea again and again across the continent, and gave rise to the accumulation of the rocks of which most of the present surface consists. In these movements the growth of the Alps and other dominant lines of elevation can be more or less distinctly traced. It was at the close of the Eocene period, however, that the great disturbances took place to which the European mountains chiefly owe their present dimensions. In the Alps we see how these movements led to the crumpling up and inversion of vast piles of solid rock, not older in geological position than the soft clay which underlies London. Considerable additional upheaval in Miocene times affected the Alpine ridges, while, in still later ages, the Italian Peninsula was broadened by the uprise of its sub-Apennine ranges. The proofs of successive periods of volcanic activity during this long series of geographical revolutions are many and varied. So, too, is the evidence for the appearance and disappearance of successive floras and faunas, each no doubt seeming at the time of its existence to possess the same aspect of antiquity and prospect of endurance which we natu-