Page:Popular Science Monthly Volume 9.djvu/329

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the northward, where it slopes more gradually beneath the inclined plane of meeting, as above explained.

For obvious reasons, the region of high barometer is within the polar current before it meets the tropical, and also within the tropical current before it is disturbed, or its horizontal movement checked by meeting the polar current; but the barometer is highest in the polar current, because it is colder and denser.

In addition to the foregoing facts which barometric observations have established, this theory of opposing currents explains a great many other aerial problems and phenomena which have not heretofore been adequately accounted for. Among these are the real causes of different kinds of storms and how they originate; why they move forward and backward, carrying the lines and areas of high and low barometer, of isobars and gradients, with them, and why they cease; why the barometer indicates the approach of some storms in advance, but is useless in others; why it falls in some storms but rises in others; why a progressive storm travels against the prevailing wind, and why the wind changes during its progress; why there is a region of calm, and why the wind is stronger around this region of calm. It explains how snow-storms change to rain, or sleet and rain, and why it falls obliquely toward the direction from which the storm is coming; also why in some storms the rain falls in advance of the area of low barometer and in the rear of it in others. It accounts for the origin of tornadoes, water-spouts, hail-storms, and all other whirling storms, and explains why these always move in an eastward direction on our continent. It explains why the rain-areas of winter storms are more extended than those of summer, why their approach is slower and their continuance longer, and why they produce sudden changes of temperature in their progress over any place. It greatly simplifies and corrects previous explanations respecting the formation of different kinds of clouds, and accounts for the development of electricity both in summer and in winter storms.



IN primitive stages of society, the clannish life of rude tribes may well have been more favorable to frank and truthful relations between man and man than our wider and looser social intercourse can be. Yet one can see, from the habits of modern savages, that already in early savage times society was setting itself to take measures against men who broke faith to save themselves from harm or to gain some coveted good. At the stage of civilization where social