In the tropics and temperate regions storms are frequently called cyclones in which the wind blows spirally
towards a centre. A cyclone is constantly moving its position, generally in a more or less easterly direction.
The approach of a cyclone is indicated by an unusually high barometer and a very clear atmosphere. Later
halos are frequently seen round the sun and moon, the barometer begins to fall, and the air becomes heavy, hot,
and moist. The barometer continues to fall rapidly and the wind freshens.