Now, we have noticed a dozen different localities, all experiencing much the same sort of storms. The unthinking person might deem all this devastation the work of a single storm. Such is the case: but a distinction must be made between the storm itself, and the tornadoes produced by it. That there were various tornadoes entirely distinct, or independent of each other, the reader may clearly perceive, by examining the foregoing pages. It will be noticed that in several cases the tornado was seen to form near the spot devastated; and further may be noted the hours at which the whirlwinds appeared. For instance, the one which passed near Shawneetown, Missouri, came later than most of those in Illinois; yet all moved toward the northeast. A brief review of the main storm will be of interest, and show how the various tornadoes were produced. It has already been stated that the storm originated somewhere about the southwest corner of Wyoming. Here, as early as Wednesday morning, the Signal Service observed an area of very low barometer. It moved rapidly eastward, with a trend toward the south, passing in the vicinity of Denver, Kansas City, and St. Louis, thence northeast through the central part of Indiana to Lake Erie. The central path of the storm was a violent and progressive movement of the air, doing in its passage trifling damage in some localities. The cyclonic movements which did the principal mischief, were all to the south of the storm center, and were local and violent motions of the air about an axis, while yet there was a progressive movement from southwest to northeast. Now, these lesser whirlwinds are produced in exactly the same way as the great cyclones of many miles in diameter, which we have already seen do not originate on land often, because of the irregularities of surface that hinder. But the local currents of wind, in meeting, produce the whirling motion. Compare with the moving of a current of water. Every river forms eddies along the bank, which move a short distance down and toward the main current, and then break up. Consider the great area of low barometer moving eastward, and it will be seen that the local tornadoes, suddenly forming and moving but a few miles, are simply eddies on its edge. It is easy to watch these produced on a small scale; for nature’s principles are the same in small and great: when we have mastered the atom, we have mastered the whole object. [Illustration: SCENE AT OLNEY, ILL.] Let one observe a great fire in a forest or prairie. On the outskirts of newly burned areas, when the air has been rarefied by heat, may be seen sudden and violent movements about a point, as though there was a spirit in the wind. In a moment it has lifted the ashes and scorched [Illustration: WHIRLWIND FROM BURNT PRAIRIE.]