Page:Popular Science Monthly Volume 22.djvu/733

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may be the capacity of the race for development in a state of peace, it is apparent, from the great check on their increase between 1860 and 1870, by the operations of the civil war, that any serious disturbance of their industrial pursuits, like a prolonged foreign war or political convulsions at home, would produce such distress as to disturb profoundly their vital movements. The same event would follow an over-production of the staples grown by their labor, owing to their habitual improvidence. Thus far they have experienced no serious rivalry, and therefore no check to their natural increase. . . . This fact is undoubtedly favorable to the numerical increase of the race, though it is equally clear that it tends at the same time to delay its intellectual improvement by deterring individuals from pursuing other and higher industries. In any event, there is little danger that either race will severely encroach on the ground of the other in our time, and no danger that the colored population of any part of the country will be in the way of the whites, unless they should so far advance intellectually and morally as to win a commanding position by sheer force of merit."

Northern Transcontinental Survey.—A "Northern Transcontinental Survey" has been organized in the interest of the Northern Pacific Railroad and its allied lines, under the direction of Mr. Raphael Pumpelly, the purpose of which is to obtain a satisfactory knowledge of the extensive, hardly explored regions which may be made tributary to those lines and their resources. It has been divided into departments of mineral resources, climate, rivers and irrigation, soils, forests, economic botany, laboratory, and topography, which have severally been put in charge of specialists. A considerable amount of preliminary work was done last year, the most important, perhaps, of which related to the examination of the black coals of the western part of the region under survey and of the brown coal-fields of Dakota. The former coals were found to be good steam-generators, the latter not, except in combination or after special preparation. Particular attention is paid to the forest resources of the country, in which we are glad to see that the economical use of the timber is not wholly left out of sight; and observations are making on the useful grasses of the country. The results of the surveys are to be cartographically represented, in a series of maps delineating severally topographical, hydrographic, climatic, and botanical features.

Langley's Observations on Solar Radiation.—The scientific expedition of Professor S. P. Langley, of the Alleghany Observatory, to the summit of Mount Whitney, in 1881, has led to some important and novel conclusions with reference to the effect of the atmosphere on the action of the sun's rays, and to the temperature of space. Among the principal objects of the expedition were, to determine how much heat the sun sends to the earth (the solar constant), and what part of the surface temperature of the planet is due to the sun's direct radiant heat, and what part to the effect of the earth's atmosphere in storing this heat. Mount Whitney, in Southern California, was chosen, because of the conveniences afforded by its great height and the dryness of its atmosphere, and because two stations could be found upon it within easy signaling distance, and yet having a difference of more than eleven thousand feet in elevation. One of the earlier observations of the expedition was to notice, as former observers had done, "that as we ascended, and the air grew colder, the sun grew hotter, till our faces and hands, browned as they already were by weeks of sunshine below, were burned anew, and far more in the cold than in the desert heat. As we still slowly ascended, and the surface temperature of the soil fell to the freezing-point, the solar radiation became intenser, and many of the party presented an appearance as of severe burns from an actual fire, while near the summit the temperature in a copper vessel, over which were laid two sheets of plain window-glass, rose above the boiling-point, and it was certain that we could boil water by the direct solar rays in such a vessel among the snow-fields." This observation induced the conclusion that if the earth's atmosphere were withdrawn, the temperature of the surface would greatly fall, though under a materially greater radiant heat; and Professor Langley expresses the opinion that