DISCUSSION OF THE VERTICAL FORCE. 



21 



ratios, it is probably due to the small number of observations, and the difficulty in 

 keeping the instrument in adjustment and allowing for its irregularities. I have, 

 therefore, given the mean ratio of the Philadelphia disturbances in the last column 

 of Table VII, and compared the result, graphically, vi'ith those deduced by General 

 Sabine for Toronto.^ 



Annual Inequality op Disturbances. 



. PhiladelpMa, 4 years. 



Toronto, 5 " 



t>> to 



> -^ ■§ d" t- aT tT 



02 O S R 



If we separate the disturbances into two parts, those increasing and those 

 decreasing the force, we obtain the numbers of Table VIII. A positive sign indi- 

 cates disturbances increasing, a negative sign those decreasing the vertical force. 

 The law of the annual variation seems to be the same as shown by the ratios in the 

 last two columns ; this accords with the result at Toronto. 



Table VIII. — Annual Inequality op Disturbances Increasing and Decreasing the Force. 





1841-42. 



1842-43. 



1843-44. 



1844-45. 



Eatios. 



+ 



- 



+ 



- 



+ 



- 



+ 



- 



+ 



— 



July 



31 



33 



8 



16 







4 



12 



10 



0.7 



1.1 



August 



14 



7 



9 



25 



8 



2 



36 



11 



1.0 



0.8 



September 



22 



18 



16 



41 



9 



11 



5 



2 



0.7 



1.2 



October 



22 



6 



8 



4 



6 



6 



3 



7 



0.6 



0.4 



November 



17 



20 



5 



8 



14 



26 



4 



1 



0.6 



1.0 



December 



51 



33 



8 



7 



23 



10 



13 



10 



1.4 



1.1 



.January 



38 



38 



32 



26 



26 



14 



6 



3 



1.5 



1.5 



February 



53 



33 



32 



19 



11 



5 



2 



1 



1.4 



1.0 



March 



16 



20 



23 



21 



30 



23 



23 



11 



1.3 



1.3 



April 



32 



19 



30 



20 



23 



19 



5 



7 



1.3 



1.1 



May 



28 



19 



18 



18 



3 



1 



11 



3 



0.9 



0.7 I 



June 



23 



14 



5 



11 



7 



19 



3 



1 



0.6 



0.8 j 



» Page Ixx., Vol. III. 



