DISCUSSION OF THE VERTICAL FORCE. 



25 



Average magnitude 43 scale divisions, the disturbances appear to be nearly of 

 the same size at all hours, there is a slight preponderance in magnitude between 

 10 A. M. and 10 P. M. over the other half of the day. 



Table XIV. — AcGRKeATE amount and mean amount of Disturbances, 

 separated into those 'whioh increase and those which decrease the 

 Vertical Force. 





Aggregate amount. 



Mean amount. 



Difference of 

 aggregate amount. 



+ 



- 



+ 



- 



0" 



2 



4 



6 



8 



10 

 Noon 

 14 

 16 

 18 

 20 

 22 



3737 

 3221 

 2866 

 2577 

 2524 

 2507 

 2731 

 4456 

 2969 

 3456 

 3003 

 3258 



3312 

 3655 

 3614 

 2841 

 2498 

 2589 

 2795 

 2645 

 2622 

 2115 

 1770 

 1988 



40 

 44 

 42 

 42 

 43 

 47 

 45 

 46 

 43 

 48 

 45 

 43 



44 

 43 

 42 

 40 

 43 

 42 

 40 

 40 

 45 

 48 

 41 

 42 



+ 425 



— 434 



— 748 



— 264 

 + 26 



— 82 

 64 



+1811 

 + 347 

 +1341 

 +1233 

 +1270 



Mean 



1 



44.0 



42.5 



+4861 



The magnitude of the disturbances, either increasing or decreasing the force, 

 apparently does not vary with the hours of the day. The disturbances which 

 increase the force preponderate between the hours 2 P. M. and 2 A. M. ; those 

 which decrease the same occur in the other half of the day, the average ratio of 

 the preponderance of increase over decrease is as 4 to 1. 



Dividing the numbers in the last column of the preceding table, or the excess 

 of the sum of disturbances increasing the force over the sum of those decreasing 

 the same, by the total number of days (1297) of observation, we find the diurnal 

 disturbance variation as follows : — 





Scale divisions. 



In parts of vertical force. 



In ab.solute measure. 



o>^ 



+0.3 



+0.00001 



+0.00013 



2 



—0.3 



—0.00001 



—0.00013 



4 



—0.6 



—0.00002 



—0.00025 



6 



—0.2 



—0.00001 



—0.00008 



8 



0.0 



-0.00000 



0.00000 



10 



—0.1 



0.00000 



—0.00004 



Noon 



0.0 



0.00000 



0.00000 



14 



+1-4 



+ 0.00004 



+0.00059 



16 



+ 0.3 



+0.00001 



+0.00013 



18 



+1.0 



+0.00003 



+0.00042 



20 



+1.0 



+0.00003 



+0.00042 



22 



+1.0 



+0.00003 



+0.00042 



Mean 



+0.3 



+0.00001 



+0.00013 



The value for the hour 14 is evidently anomalous, the mean of the hours 12 and 

 16 or + 0*.2 (0.00001 in parts of force, 0.00008 in absolute measure) should be 

 substituted. The average daily effect of the larger disturbances is therefore to 

 increase the vertical force between 1 P. M. and midnight, and to decrease it 



