52 



DISCUSSION OF THE VERTICAL COMPONENT 



647 

 49 

 51 

 53 

 55 

 57 

 59 

 61 

 63 

 65 

 67 

 69 

 71 

 73 

 75 

 77 

 79 

 81 



Diagram (F). 



r— / 



-t 



/ 



/ 



'■jsla' 



A 



A 



-/- 



^ 



/ 



/ 



// 



// 







664 





66 





68 



92 



70 



94 



72 



96 



74 



98 



76 



700 



78 



02 



80 



04 



82 





84 





86 





88 





90 





92 



2 4 6 8" A. M. 



Pliiladelphia mean time. 



Table VII exhibits the computed times of the principal maximum and minimum 

 of the vertical force, together with the amount of difference from its average daily 

 value at these epochs, expressed in scale divisions ; also the time and amount of 

 the early morning secondary fluctuation traceable only in the winter months ; for 

 these last values the diagrams have been made use of. 











Table 



VII. 















Maximum 

 at 



Amount in 



scale 

 divisions. 



Minimum 



Ht 



Amount in 

 scale 



Time elapsed 



between 

 max h min. 



Secondary 



maximum 



at 



Amount. 



Secondary 



Minimum 



at 



Am't. 



Secondary 

 rant:e. 



January 



February 



March 



April 



May 



June 



July 



August 



September 



October 



November 



December 



13" 07°' 

 13 41 



12 46 



13 52 



14 34 

 13 09 

 13 33 

 13 02 

 13 23 



11 16 



12 35 

 12 31 



— S'i.S 

 —11.5 



— 8.9 

 —10.2 

 —13.1 

 —17.2 

 —18.2 

 —20.8 

 —16.8 



— 7.6 



— 7.4 



— 7.8 



19''27'» 



20 21 



21 04 



22 04 

 22 58 



22 35 



23 10 

 23 06 

 23 20 

 20 34 

 19 59 

 19 09 



+ 9^.4 

 +10.6 

 + 6.7 

 +11.8 

 +12.6 

 +16.2 

 +17.3 

 +15.5 

 +12.6 

 + 8.7 

 + 3.9 

 + 7.8 



6i> 20" 



6 40 



8 18 

 8 12 



8 24 



9 26 

 9 37 



10 04 

 9 57 

 9 18 



7 24 

 6 38 



21" 



1.4 



3 



—4 



+ 1 

 —1 



7" 

 4.V 

 ^. 



+2 

 +4 

 +2 



6 



3 

 3 





















































2 

 1 

 3 



—1 

 +1 

 —3 



5 



7 



+1 

 + 3 

 -1-1 



2 

 2 

 4 



Summer 



Winter 



Year 



13 29 



12 43 



13 02 



—15.8 

 — 8.2 

 —11.9 



22 55 



20 08 



21 25 



+14.1 

 + 7.6 



+ 9.7 



9 26 



7 25 



8 23 













2 



—1 



6 



+2 



3 













The extreme variation in the time of the maximum in the course of a year is 

 S*" 18", and of the minimum ^ 11'". 



At Toronto the occurrence of the maxima and minima is later than at Phila- 



