10 



ANALYSIS OF THE 



The inequality of the eleven year period is equally well marked for disturbances 

 increasing and for disturbances decreasing the total force. 



The sum of the positive values is 1.03744, and of the negative values 0.80046 ; 

 increasing disturbances are therefore preponderating in the ratio of 1.3 to 1. In 

 the year 1842-1843, however, decreasing disturbances were in excess over increas- 

 ing ones, and at Toronto between 1844 and 1848, the general effect of the larger 

 disturbances of the force was to decrease the total magnetic force more than to 

 increase it. The excess in the different years appears to be rather irregular. 



The following tables exhibit the diurnal inequality of the disturbances, the* 

 whole series (beginning with February, 1841) is employed. The sums, numbers, 

 and ratios given apply to an epoch 20 minutes later than indicated by the tables. 



The hourly disturbances exhibit a regular double progression with a principal 

 maximum at 2 A. M., and a principal minimum at 8 P. M., also a secondary maxi- 

 mum about 2 P. M., and a secondary minimum abut 10 A. M. At Toronto these 

 hours were respectively 3 A. M., 11 A. M., and 5 P. M., 9 P. M., showing an ex- 

 change of the hours of the principal and secondary minimum ; the disturbance at 

 the hour of maximum is about eleven times greater than at the minimum hour, 

 whereas this proportion is but one and a half to one at Philadelphia. 



