32 DIP AND TOTAL FORCE. 



From what has been said of the annual inequality of the horizontal and vertical 

 force, it could not be expected that this inequality should appear in any decided 

 manner in the dip and total force. With reference to the dip, aU that can be 

 concluded is, that the iirequality probably does not exceed half a minute. At 

 Toronto, where the dip is greater, it is between 0.'8 and 0.'9; lower in June and 

 July than in January and December; range 1.'7. With respect to the total force, 

 the inequality seems to be about 0.0003 parts of the force, which gives nearly the 

 same range as that found at Toronto, with this difference, however, that at Phila- 

 delphia the force is greater in the summer months and less m the winter months, 

 the reverse of what has been foimd at the other station. 



The next and last part of tlie discussion of the Girard College Magnetic Observa- 

 tions will contain the absolute values of the magnetic declination, dip and intensity. 



