In England out of a _thousand days_, north winds prevail in 82; north-east, 111; east, 99; south-east, 81; south, 111; south-west, 225; west, 171; north-west, 120. 676. _What is the cause of storms?_ Storms result from violent commotions of the atmosphere, and are chiefly the result of extreme _changes of temperature_. The _magnetic_ state of the earth, and the _electrical_ state of the atmosphere, also materially influence the phenomena of storms. By some persons the theory is entertained that storms result from various winds _rushing into a centre_ in which the atmosphere has become extremely condensed. According to this theory, a storm is a mighty whirlwind. A most violent hurricane occurred in 1780, which destroyed Lord Rodney's fleet, and a vast number of merchant ships. It is said to have killed 9,000 persons in Martinique alone, and 6,000 in St. Lucia. The town of St. Pierre in Martinique was totally destroyed; and only fourteen houses in the town of Kingston, in St. Vincent, were left uninjured. 677. _Why do the most violent storms occur in and near the tropics?_ Because there the temperature is very high, and the cold currents of air rushing towards the equator from the poles, causes great _atmospheric disturbance_. 678. _What are whirlwinds?_ Whirlwinds are produced by violent and contrary currents meeting and striking upon each other, producing _a circular motion_. They generally occur after long calms, attended by much heat. Whirlwinds occurring at sea, or over the surface of water, sometimes put the water in motion, and as the wind rises upwards it lifts with it a whirling mass of water, producing a _water spout_. [Verse: "Out of the south cometh the whirlwind; and cold out of the north."--JOB XXXVII.] [Illustration: Fig. 19.--A WATER SPOUT.] 679. _Why does the chimney smoke when the fire is first lighted?_ Because the air in the chimney is of the same temperature as that in the room, and therefore _will not ascend_. 680. _Why does the smoking (into the room) cease, after the fire has been lighted a little while?_ Because the air in the chimney, being warmed by the fire beneath, becomes lighter and ascends rapidly. 681. _Why does a long chimney create a greater draught than a short one?_ Because the short chimney contains _less air_ than the long one; there is, consequently, less difference of weight between the warm air of the short chimney and the external air; it therefore has not so great an _ascensive power._ [Verse: "And, lo, the smoke of the country went up as the smoke of a furnace."--GEN. XIX.] 682. _Why does smoke issue in folds and curls?_ Because it is _pressed upon_ by the _cold air_ which always _rushes towards a rarer atmosphere_. It thus illustrates the development of _storms_. 683. _Why do some chimneys smoke when the doors and windows are closed?_