Over the large land areas of the north temperate zone highs and lows show a tendency to travel over typical tracks, the locations of which vary a good deal with the season. One of the most remarkable facts about the lows of North America is that, wherever they come from, whether from the Canadian northwest, the western United States, or the West Indies, they nearly always leave the continent by way of the Gulf of St. Lawrence or the northeastern corner of this country. Our North American lows travel at an average speed of 600 miles a day. Highs travel somewhat more slowly; about 540 miles a day is the average in this country. A _tornado_ is a small vortex in the atmosphere, occurring generally in the southeastern part of a cyclonic area, where, in some cases, several separate tornadoes develop at the same time. The tornado, for some reason that is not altogether clear, is far more common in the interior of North America, east of the Rocky Mountains, than anywhere else in the world, though true tornadoes do occur in other countries. The West African storms bearing this name are merely thundersqualls, quite different from the American tornado. The chief visible feature of a tornado is the so-called funnel-shaped cloud (sometimes balloon-shaped or, again, like a great coiling serpent), which is always in contact with the ground when destruction is in progress. The passage of the storm is attended by a loud roaring or rumbling. The path of a tornado varies in width from a few rods to half a mile or (rarely) more. Within its borders buildings are blown to pieces, trees are uprooted and human beings only find safety underground; while even at a distance of a few yards outside the path no damage is done. The tornado travels at an average speed of about twenty-five miles an hour. Its speed of rotation has been estimated, from the effects produced, to amount to 500 miles an hour in some cases; a wind force far exceeding that of any other type of storm. _Waterspouts_, which occur on the ocean and other large bodies of water, are similar in character to tornadoes, though much less violent. They range in height from 100 to 1,000 yards, or more. One measured recently from the British steamer _War Hermit_, near Cape Comorin, was 4,600 feet high to the base of the overlying cloud. The column tapered from 500 feet wide at the junction with the cloud to 150 feet wide at the sea. Spray was thrown up to a height of more than 800 feet over a region 250 feet in diameter.