CYCLONE (Gr. KVKAwv, whirling, from KbK)^os, a circle)  , an atmospheric system where the pressure is lowest at the centre . The winds in consequence tend to blow towards the centre, but being diverted according to Ferrel's law they rotate spirally inwards at the surface of the earth in a direction contrary to the movement of the hands of a watch in the northern hemisphere, and the reverse in, the southern hemisphere . The whole system has a motion of translation, being usually carried forward with the great wind-drifts like eddies upon a swift stream . Thus their direction of movement over the British Islands is usually from S.W. to N.E., though they may remain stationary or move in other directions . The strength of the winds depends upon the atmospheric gradients .