1869.] 



Dr. B. Stewart on the Kew Magnetic Curves. 



467 



It will be seen from this Table that there is great constancy in the type 

 of the peak-and-hollow force for the same hour. Bearing in mind the 

 difficulty of finding exactly similar appearances denoting an unmixed force, 

 and remembering also the small size of many of the peaks and hollows 

 observed, it is not too much to say that, as far as these two years' obser- 

 vations are concerned, there is no trace of anything else than a diurnal 

 change in the type of the peak-and-hollow force. But this question can- 

 not be finally decided until more observations are discussed. 



In the following Table the final results of Table II. are brought before 

 the eye in a condensed form.. 



Table III. 



Hourly Ratios and Frequency of the Peaks and Hollows, the vertical force 

 being taken as unity. 



Hour. 



Declination. 



Horizontal force. 



Mean of both years 



I 



Number 











Declina- 



Horizon- 



of obser- 













vations. 





1858-59. 



1859-60. 



1858-59. 



1859-60. 



tion. 



tal force. 



O-I 



1-97 



2-32 



2*00 



2-13 



2-14 



2*06 



7 



1-2 



2*19 



176 



2'33 



2*00 



r 97 



2-16 



7 



2-3 



1*92 



i-8i 



2 - 00 



r 9 8 



r86 



r 9 9 



1 1 



3-4 



r8 4 



178 



2-17 



1 -93 



r8i 



2*05 



7 



4-5 



1-50 



1-27 



i-8o 



r6 7 



r 3 8 



i'73 



4 



5-6 



1-57 





171 











6-7 

















7-8 



i'6o 



2-04 



2'20 



1-62 









8-9 



1 60 



2'20 











9-10 

















10- 1 1 



i-33 





3 -i6 











1 1-12 



1-29 





2*14 



2*50 









12-13 



176 



2-68 











I3-H 



2-QO 





2-04 











14-15 



2 '2 I 



1*90 



2-18 



2'IO 



2"IO 



2-14 



5 



1 5-16 



3"o6 



2-25 



2-15 



Z'OJ 



2*65 



211 



10 



16-17 



3*59 



3*37 



2*25 



Z'OJ 



3-48 



216 



15 



17-18 



375 



3-85 



2-19 



2*09 



3-80 



2-14 



22 



18-19 



4-06 



3-82 



2-22 



2-14 



3*94 



2-18 



28 



19-20 



3 "49 



4*45 



2*23 



2-27 



3'97 



2-25 



21 



20-21 



3-21 



3-6i 



2-26 



2'l6 



3'4 r 



2'2I 



23 



21-22 



3'4° 



3'i3 



2*36 



2*24 



3*26 



2*30 



16 



22-23 



2*40 



3'i9 



2*03 



K96 



279 



2 - 00 



10 



23-0 



2*58 



2*03 



1-99 



2*IO 



2-30 



2*04 



.3 



From this Table it will be seen that, as was formerly stated, the ratio 

 between simultaneous peaks and hollows of the two components of the 

 force is very nearly constant, the horizontal force disturbance being very 

 nearly double of that of the vertical force. 



It will also be seen that there is a very marked diurnal range in the 

 ratio which the declination peak or hollow bears to that of the vertical 

 force, this ratio being greatest about 7 a.m. About this hour we have 

 also most peaks and hollows, while in the evening and very early morning 



VOL. XVII. 2 M 



