112 Senhor Capello and Mr. B. Stewart — Comparison of [Jan. 28, 



The disturbance, which began iu this manner, continued until July 25th, 

 if not longer ; but during the period of its action there was not for any of the 

 elements a very great departure from the normal value ; probably in this 

 respect the declination was more affected than either of the other com- 

 ponents. 



While frequently there is an amount of similarity between the different 

 elements as regards disturbances of long period, yet there is often also a 

 want of likeness. If, however, we take the small but rapid changes of 

 force, or peaks and hollows, as has been done by one of the writers of this 

 paper in a previous communication to the Royal Society (Phil. Trans. 1862, 

 page 621), we shall find that a disturbance of this nature which in- 

 creases or diminishes the westerly declination at the same time increases or 

 diminishes both elements of force. This will be seen more distinctly from 

 the following Table, in which +]denotes an increase and — a diminution of 

 westerly declination, horizontal, and vertical force respectively, and the pro- 

 portions are those of the apparent movements of the elements on the pho- 

 tographic paper. 



Table I. 



Date. 



Greenwich 

 Mean Time. 



Declination. 



Horizontal 

 force. 



Vertical-force 

 change = unity 

 in each instance. 



1863. 











July 17 



2 46-5 



— i-o 



-1-9 



— i*o 



17 



2 53'5 



— I'l 



— 2'0 



— I'O 



17 



3 21*5 



— i-o 



— 2*0 



— I-o 



17 



7 58-5 



not similai*. 



— 2*0 



— I'O 



17 



16 13-0 



+ 3-5 



+ 2'2 



+ ro 



18 



21 23-5 



+ 3-0 



+ 2*0 



+ ro* 



19 



15-5 



not similar. 



+ 1-8 



-fro 



19 



2 i3'5 



+ ri 



+ 1-9 



+ ro 



19 



2 38-0 



+ ri 



+ 17 



+ ro 



19 



3 22-5 



+ ro 



+ 1-9 



-f-ro 



19 



17 51-0 



+ 2-8 



+ 2'0 



+ rot 



19 



18 o"o 



+ 3-6 



+ 2-0 



+ rot 



19 



20 29"5 



+ 3-2 



+ 2"0 



+ I-0 



20 



3 2I*0 



+ ro 



-l-r6 



-fro 



20 



18 52-5 



+4"o 



+ 2*2 



-fro 



21 



22*0 



-1-6 



-2-3 



— I-o 













21 





-1-4 



— 2'I 



— I'O 





[ 2 I5'0 1 









21 



5 38-0' 



+ 1-4 



+ 2"0 



-fro 



22 



19 20'5 



-4-0 



— 2'0 



— I'O 



22 



19 32-5 



-3"4 



— 2'0 



— I'O 



22 



21 40-0 



+ 3-5 



-|-2-0 



-fro 



n 



18 34*5 



+ 3-5 



-f2-2 



-fro 



23 



19 26-5 



+ 3-4 



H-2'O 



+ i'ot 



24 



3 31-0 



+ 1-2 



-i-2"0 



-fro 



24 



16 44'5 



+ 3-1 



4-2*0 



4- 1 -of 



* Doubtful. t Vertical force too small to be accurately measured, but horizontal- 

 force change reckoned =2'o. 



