DISTURBANCES OF THE INCLINATION. 



The hourly disturbances of the inclination exhibit a regular progression ; between 

 1 A. M. and 1 1 A. M. the numbers fall short of the mean hourly value, and during 

 the remaining afternoon and night hours they exceed this average value. The 

 minimum occurs near 8 A. M. and the maximum near 8 P. M. There is, however, 

 an indication of a superimposed smaller progression which, owing to the short series 

 of observations, is not distinctly brought out. At Toronto we have a double pro- 

 gression, and the above ratios approximate to it. At Philadelphia a secondary 

 maximum probably occurs about noon and a secondary minimum about 4 P. M. 



Table VI shows the ratios at the different hours for disturbances increasing and 

 disturbances decreasing the inclination. 



The disturbances which increase the inclination show a very regular single pro- 

 gression (the value at 2 P. M. only being slightly anomalous) ; their minimum 

 occurs at 4 A. M., and their maximum at 8 P. M. The disturbances decreasing the 

 inclination are small in number at all hours, and show a tendency at double pro- 

 gression ; principal maximum about noon, principal minimum about 8 P. M., second- 

 ary maximum about 4 A. M., and secondary minimum about 8 A. M. At Toronto 

 the results appear different, but it is absolutely necessary for effective comparison 

 to have results from contemporaneous series. As at Toronto, the disturbances increas- 

 ing the inclination greatly preponderate over those decreasing it ; the accumulated 

 effect of this difference is shown in the column headed " Excess" (Table VI). At 

 the hour 4 A. M. alone, we find the increasing disturbances inferior, at the hour 8 

 P. M. the difference has reached its maximum ; at Toronto this maximum occurred 

 an hour or two after midnight. The last column of Table VI exhibits the average 

 diurnal effect of the disturbances (exceeding l.'l their normal value), the plus 

 sign indicating a preponderance of increasing dip ; the number of days is 1297. 



The distribution of the disturbances according to their magnitude for an equal 



increase of 1' is as follows: 

 11 



