56 



DISCUSSION OF THE VERTICAL COMPONENT 



(H). Differences from its Normal Value of the Vertical Force, for each Hour and MoNfH. 



(Expressed in absolute measure.) 

 0.00. 



January 



14 16 18 20 22 



Philadelphia mean time. 



Annual Inequality of the Vertical Force. — The minor and irregular disturbances in 

 the adjustment of the magnetometer, as well as the effect of the progressive and 

 secular changes, tend to make the determination of the annual inequality in the 

 vertical force a task of some delicacy, and the results deduced from our series of 

 observations should be considered as approximate. 



Taking the monthly normals of the years 1842, 1843, and 1844, the only years 

 which could be made complete, and correcting the monthly means for 42 scale 

 divisions of annual increase, the following table was formed : — 



