east of Ercildoun, and proceeded, at a higher elevation, for about seven miles, relieving the farms and property of the intervening country from destruction. As it approached Broad Run, about a mile west of Marshallton, it descended sufficiently long to unroof and almost destroy the barns and out-buildings of two properties, owned respectively by Richard Baily and Joseph Marshall, of West Bradford township. Here it came to an end in its mad and reckless career. The two opposing currents of air had no doubt now become thoroughly blended and partook of the character of a high wind, fully relieved of its devastating properties. The storm-cloud was dissolved, or had permanently taken a higher elevation over a still greater amount of territory. The whole route of the tornado, as measured by its effects, was about 22 miles. The width of its track was from 100 to 300 yards, averaging generally about 200 yards. The following points also have been pretty clearly established by the use of the compass, and also by careful observation along the route of the storm:

First. That the general direction of the storm-cloud during the first half of its journey, to a point near Newlin's Mill, one mile west of Ercildoun, was south 75 deg. east, but at that point it changed and its course afterwards was south 83 deg. east, or nearly due east. Second. That the destruction of property was generally greater as the cloud moved across a valley. Third. That the velocity of the moving mass varied at different periods from 5 to 15 miles an hour, but twelve miles an hour would be considered a fair average. Fourth. That the trees along the southern side of the track of desolation were generally thrown with their tops towards the north, or at right angles to the direction of the progressive motion of the cloud, while those on the northern side were thrown in the opposite direction. Fifth. That in some instances houses and buildings near the centre of the track were but slightly injured. These cases, however, were rare. Sixth. That from local and other causes, the lower part of the conical cloud frequently moved out of a straight course, while the upper or larger part of the cone kept in a line very nearly direct. Seventh. That as soon as the cloud was formed, a roaring sound commenced, which continued without interruption during its entire course. This sound was not unlike continuous thunder. Eighth. That the movement of the storm-cloud was unaccompanied with much rain or hail, though one or the other fell at some distance north or south of the track, the sun frequently shining at the time. To explain some of these phenomena, even with the aid of science, is difficult. The storm-cloud itself was an entirely exceptional phenomenon in this latitude. Such an event had never occurred before in eastern Pennsylvania, and we are without the benefit of previous observation and experience. The great destruction of property in crossing valleys has excited marked attention. The cloud undoubtedly required an immense amount of air to feed it as it went along. Persons near its track say that they breathed with the greatest difficulty. The surrounding air must have been very rare; in fact, a partial exhaustion must have resulted from the absorption of air by the moving mass. In crossing a valley at right angles, or nearly so, the dense air up and down on either side, would be at hand to furnish it with the necessary material, thus increasing its power and devastation; this is one explanation. Another theory, which is probably the correct one, could safely be advanced upon plausible grounds. Supposing electricity to be the primal cause of the cloud itself, in passing across deep and irregular valleys with rugged surface, more electricity would be developed, and greater power would be infused into the revolving cone as it moved forward. When passing over a smooth, level plateau, it would excite less of the electrical fluid, and would hence be disarmed of a portion of its ability to destroy buildings and fences.

The second important point that we must consider is the increased destruction of property and great violence exhibited on the right side of the centre of the revolving axis of the storm-cloud, and a corresponding diminution of destructive power on the left side. The movement of the whirl was undoubtedly from right to left; the fallen trees indicate it. The forward motion of the hurricane would create a great inrushing of wind on the right side, and greater damage would result than upon the other side where the wind was returning to complete the rotary movement. While it is true the trees were overthrown to some extent in all directions, yet they mostly fell in the direction in which the wind struck them as it moved around in its whirling motion. The southern side of the track of desolation, however, presents evidence of the greatest power. The maple and other forest trees were frequently twisted entirely off, showing conclusively, that while they were first struck by the progressive motion, the rotary motion was sufficiently quick to locate the falling trunk. The great power of the storm-cloud was due to its revolution. In fact, this marks the difference between the high wind and the hurricane or tornado. The phenomena observed in connection with the storm of July first, are almost identical with those of similar character in the Southern States and West Indies.

The third subject presented for our consideration is the upward and downward currents which seemed to exist within the cloud. Objects were thrown upward to an immense distance, and the distance to which some objects were driven into the earth must convince us that there was a force downward of great power. It is true that a falling body, when influenced by gravity alone, will descend with great force, especially if started from a high point, but the deep excavations found in the track of the storm can only be accounted for by a downward current. The funnel-shaped cloud enlarging its circumference towards the top, would, with its centrifugal force resulting from its revolution, hurl bodies to a great distance, and we find the debris of this tornado hundreds of yards outside of its track, proving that when an object was carried up in the whirl, it was often thrown off, laterally for a great distance. A remarkable feature in connection with the tornado is the preservation of buildings in the track of the storm. Property on both sides of a house was sometimes destroyed, and yet the building itself was scarcely injured. This gap in the storm must have occurred from local causes, and from the gradual elevation and descent of the progressive movement of the cloud, thus carrying it over and beyond some of the objects in its track. Some cases of this character will be mentioned in the subsequent pages of this book.

The color and appearance of the storm cloud is worthy of consideration. By some who viewed it as it passed along, it is represented as being an immense balloon, extending to the height of several hundred feet, spreading out at the top, forming a funnel. It moved along at times with great rapidity, and at other times it seemed to halt, as if gathering strength for another effort. The color was variegated, the whole presenting rather a luminous appearance. Missiles of every kind could be distinctly seen in and through the body of the cloud. At first sight it seemed to be a barn on fire—the burning embers flying in every direction; but a closer inspection proved it not to be fire, but dirt and hay and timbers, intermingled with leaves and other light substances, giving it the appearance of an immense wind storm, which was the correct conclusion. Those who had a side view of the cloud state that it was quite light in appearance as it passed over grass fields and timber tracts, but when it reached a plowed field or a potato patch, it gathered up the