23G Dr. B. Stewart on Observations of Dip [Mar. 3, 



Table III. 



Date. 



Observed secular change. 



Observed minus average 

 secular change. 





i 



231 



1 



4-0-24 







— 0*92 





2-12 



+ 0-05 





1-87 



— 0'20 





2-53 



+ 0-46 





318 



+ I-U 





2-40 



+0-33 





o-8i 



— 1-26 





3-06 



+0-99 





2-82 



+075 



1867-68 



0-49 



-I-it 



If we take the first three and the last two of the above differences as 

 belonging to the years when the disturbances were increasing, we find a 

 secular change less than the average by a mean of 0'*29 ; and if we take 

 the remaining six differences as belonging to the years when the disturb- 

 ances were decreasing, we find a secular change greater than the average 

 by a mean of 0'*24. 



It would therefore appear that the Kew observations present a pecu- 

 liarity similar to those at Toronto, so that the difference of l'*69 between 

 the two sets of observations may probably be accounted for by this cause. 



10. We may, in fact, exhibit the peculiarities of the graphical represen- 

 tation given above by means of the actual results. Thus, if we take the 

 first year's dip (1857), or 68° 24'*87, and deduct from it every year 2'*07 

 (which is the average secular change), we shall obtain a series of yearly 

 values representing the yearly positions of the line AED ; and if the 

 diagram truly represents the facts, the observed yearly values ought to range 

 above the line for the first six years, and under it for the second six. 



We may see by the following Table that this is actually the case : — 



Table IV. 



Observed yearly 

 values 

 (1). 



o 

 6S 



68 



24-87 

 22-56 

 21-41 

 19-29 

 17-42 

 14-89 

 11-71 



931 



8-50 



5 '44 

 2-62 

 2-13 



Yearlv values of 

 AED 

 (2). 



68 24-87 



22*8o 

 20-73 



18-66 

 16-59 

 14-52 

 12-45 

 10-38 

 831 

 6-24 



4-i7 

 2-13 



68 



(l)-(2). 



o 



— 0*24 

 4-o-68 

 +0-63 

 +0-83 

 +0-37 

 -0-74 

 — 1*07 

 4-0-19 



— o-8o 



-i-55 

 o 



