DISCUSSION OF THE YERTIOAL FORCE. 



23 



1841, to June, 1845, omitting only the single daily observation in January, Febru- 

 ary, and March, 1843. Strictly speaking the time is 21 minutes later than indicated 

 in the table. 



Table XI 



— Diurnal Inequality in the number op Disturbances. 1 



The ratios of the three elements have been collected to facilitate comparison. 1 







Ratios. 1 





Numter 

 vertical force. 



1 













Vertical force. 



Horizontal force. 



Declination. 



0" 



168 



1.3 



1.1 



1.0 



2 



159 



1.2 



0.9 



1.2 



4 



156 



1.2 



0.7 



1.0 



6 



133 



1.0 



0.7 



1.1 



8 



117 



0.9 



0.8 



• 1.0 



10 



115 



0.8 



1.1 



1.1 



Noon 



131 



1.0 



1.3 



0.9 



14 



163 



1.2 



1.0 



0.8 



16 



127 



0.9 



1.1 



0.9 



18 



116 



0.8 



1.1 



0.9 



20 



110 



0.8 



1.1 



1.0 



22 



123 



0.9 



1.1 



1.1 



Mean 



135 



1 



The greatest number of disturbances occur about A. M. (at Toronto at 3 A. M.), 

 with the least number at 10 A. M. (at Toronto at 11 A. M.); the secondary maxi- 

 mum and minimum occur about 2 P. M. and T P. M. (at Toronto the hours are 5 

 P. M. and 9 P. M.). On the average, therefore, the maxima and minima occur 1*^' 

 40" earlier at Philadelphia than at Toronto. At neither station do the three ele- 

 ments show the same law; they agree only in so far as to exhibit a systematic in- 

 crease and decrease with the solar hours, and in having two maxima and two minima. 



The diagram shows the law of the disturbances of the vertical force for Phila- 

 delphia and Toronto. 



Diurnal "Variation op Disturbances. 



Philadelphia, 4} years. 



Toronto, 5 " 



1.6 

 1.5 

 1.4 

 1.3 

 1.2 

 1.1 

 1.0 



\a 



\ 





A 





, 





- 





v./ 



> 



/ 



/ 





V 



- 



0" 2 4 6 8 10 a 14 16 18 20 22 24" 



