24 



DISCUSSION OF THE VERTICAL FORCE 



The laws which regulate the diurnal occurrence of the nnmber of disturbances, 

 increasing and decreasing the vertical force, are evidently not the same, yet they 

 are by no means the converse of one another as has been found to be the case in 

 the disturbances of the declination and the horizontal force. At Toronto also, 

 where the horizontal force and declination curves were exactly opposed, that of the 

 vertical force is not so, and at Philadelphia rather favors an agreement between the 

 increasing and decreasing disturbances than an opposition. 



Principal maximum of increasing disturbances 2 P.M., principal minimum 9 A.M. 

 (at Toronto 5 P. M. and 5 A. M. respectively). Secondary maximum at midnight ; 

 this may possibly be the principal maximum ; secondary minimum at 8 P. M. 



Principal maximum of decreasing disturbances 4 A. M., principal minimum 8 

 P. M. (at Toronto 3 A. M. and 6 P. M. respectively). The secondary maximum at 

 noon is less distinctly marked ; secondary minimum at 8 A. M. 



Thus the epochs of the curves for increasing and decreasing force seem to be 12 

 hours apart. 



Diurnal Inequality in the Magnitude of the Disturbances. 



