CHAP. 6. OF WINDS. 201 



be from East, but North East; and the number 

 of degrees North of the East from which it 

 will blow will depend upon the comparative 

 force of the current of air from the North to the 

 difference between the Earth's motion at the 

 equator and at the polar region, from whence the 

 air comes. As there must be a corresponding 

 efflux from the equator higher up ; according 

 to this theory, the Wind should every where 

 be North East or South West ; but it blows 

 in very different directions at different times 

 and places ; and this probably depends on the 

 variations in temperature at different times 

 and places. 



To partial rarifactions we must ascribe the 

 gales which blow in mountain valleys. I 

 noticed, in traversing the Jura, July 29, 182^2, 

 that the Valley Gales Avere much stronger 

 about half way up, than at the highest parts of 

 the Mountain. 



I shall not enter into the detail of the subject, 

 but refer to several treatises written on Winds 

 by different authors.* 



* Since the publication of the first edition of this work, I 

 have made many experiments with Balloons, and have observed 

 them always to move in two or more currents, whenever the 

 Wind was not so great as to carry them soon away from 

 sight. 



