66 PROF. BALFOUR STEWART AND MR. W. DODGSON ON 



now attempt a reproduction of the past, and perhaps even 

 a forecast of the future, as far as declination-range is 

 concerned. 



The calculations necessary for this are given in Table 

 IV. ; and a graphical comparison of the observed and cal- 

 culated results will be found in the diagram (p. 69). 



The mean difference between observed and calculated 

 results is 39" ; but there is reason for supposing that ulti- 

 mately a still nearer approximation will be obtained. 



On the whole this is a good agreement ; and the result 

 appears to us in favour of the hypothesis that the long- 

 period inequalities of declination-range exhibit a true 

 periodicity. Nevertheless, owing to paucity of material, 

 this analysis is by no means complete. 



It will be seen that while there is, according to our cal- 

 culation, the probability of a maximum about 1884, it will 

 not be so high as that in 1 8 7 1 , and we shall afterwards 

 enter on a period of diminished magnetic, and probably 

 diminished solar action. Something of the kind was sus- 

 pected by the late Mr. Broun. 



Table IV. * 













ttf) 







Declination. 















10 













Year. 



I2'0. 



10-5. 



16-25. 



Sum. 



O 



03 





 X 



p 



^6 



> 





 a 













^ 



bO 



M 



d 



?h 



N 

















""ea 



PI 



c3 



^3 





 1 — 1 



c3 



GO 



£ 

















ti 



<l 



O 



O 



A 



1784. 



-3-98 



+0-30 



—072 



-4'4° 



197 



10-65 



2972 



25'3 2 



23-76 



+1-56 



1785. 



2'26 



2-66 



0-63 



°' 2 3 



197 



10-65 



29-72 



29-49 



26-IO 



3'39 



1786. 



C09 



4-38 



+ o-86 



+ 5-I5 



18-8 



10-16 



29-23 



34-38 



34^5 



0-23 



1787. 



+ 272 



3*«7 



3*16 



975 



18-2 



9-84 



28-91 



38-66 



3878 



— - I2 



1788. 



4.II 



1-63 



1-98 



772 



17-1 



9-24 



28-31 



36-03 



34'45 



+ I-58 



1789. 



2-80 



0*27 



3-19 



6-26 



16-1 



8- 7 o 



27-77 



34 - °3 



34-78 -075 



1790. 



1-52 



-197 



2 *33 



i-88 



14-9 



8-05 



27*12 



29-00 



33-26 



4-26 



* In this table the previous sign is supposed to be repeated until a new- 

 one is given. 



