DISCUSSION OF THE VERTICAL COMPONENT 



Subtracting each value of Table I from its respective monthly mean as given in 

 Table II, and converting the remainder into parts of the force, we find the regular 

 solar-diurnal variation presented in the following table : 



Multiplying the above numbers by Y=12.83, we obtain the solar-diurnal varia- 

 tion in absolute value. 



Annual Inequality in the Diurnal Variation of the Vertical Force. If we examine 

 the average curve of the diurnal variation as observed throughout the year, and 

 shown on diagram (A) by a full black line, we find the principal maximum value 

 about 1 P. M., and the principal minimum value about 9| P. M. ; besides these 

 characteristic values there is an indication of a secondary maximum about 2 A. M., 

 and of a secondary minimum about 4 A. M. Dividing the year into a summer 



