18 



DISCUSSION OF THE VERTICAL FORCE. 



INEQUALITY IN THE DIURNAL VARIATION OF THE VERTICAL FORCE. 



87 

 89 

 91 

 93 

 95 



697 14 



99 16 



01 18 



03 20 



05 22 



07 24 



26 



28 



40 730 

 42 32 

 44 34 

 46 36 

 48 38 

 SO 40 

 52 42 

 64 



756 

 68 

 60 

 62 

 64 

 66 



29 

 31 

 33 

 35 

 37 

 39 

 641 

 43 

 45 

 47 

 49 

 51 

 53 

 55 



1841-42. 



1842-43. 



1843-44. 



1844-45. 



-a 



O h 2 4 6 8 10 12 14 16 18 20 22 24" 

 (A.M.) (P.M.) 



Philadelphia time. 



The epochs are given to the nearest quarter of an hour. 



If we compare the Philadelphia and Toronto curves, we find a general corres- 

 pondence in their form, the early morning secondary in flection being well exhibited 

 at Toronto ; the epochs of the two curves, however, are shifted by nearly three 

 hours, thus: at Toronto principal, maximum at 5 P. M., at Philadelphia \\ P. M. ; 



