DOUBLE MOTION OF HUEEICANES. 



285 



the very centre of the hurricane the atmosphere remains perfectly 

 calm ; a terrible peace, a formidable silence, reign in the changing 

 circle formed by the raging whirlwind of the tempest. 



If the cyclone turned round in its place, the wind would blow 

 exactly in the direction of the tangent over the whole course of the 

 storm ; but it is not thus because of the double movement of the 

 hurricane ; while revolving it moves on, and consequently the di- 

 rection of the wind must be the result of the two forces which bear 

 it along. Let the entire whirlwind be directed towards the west, and 



Fig. 115.— Parabola described by a hurricane (after Bridet). 



