In front of the storm the warm and generally moist relatively warm air, pressing in toward the point of uprise and overlaid by the upper cold air, is brought into a condition where it tends to form small subordinate shafts up through which it whirls on the same principle, but with far greater intensity than the main ascending column. The reason for the violence of this movement is that the difference in temperature of the air next the surface and that at the height of a few thousand feet is great. As might be expected, these local spinnings are most apt to occur in the season when the air next the earth is relatively warm, and they are aptest to take place in the half of the advancing front lying between the east and south, for the reason that there the highest temperatures and the greatest humidity are likely to coexist. In that part of the field, during the time when the storm is advancing from the Rocky Mountains to the Atlantic, a dozen or more of these spinning uprushes may be produced, though few of them are likely to be of large size or of great intensity. The secondary storms of cyclones, such as are above noted, receive the name of tornadoes. They are frequent and terrible visitations of the country from northern Texas, Florida, and Alabama to about the line of the Great Lakes; they are rarely developed in the region west of central Kansas, and only occasionally do they exhibit much energy in the region east of the plain-lands of the Ohio Valley. Although known in other lands, they nowhere, so far as our observations go, exhibit the paroxysmal intensity which they show in the central portion of the North American continent. There the air which they affect acquires a speed of movement and a fury of action unknown in any other atmospheric disturbances, even in those of the hurricanes.