400 



Prof. B. Stewart on 



[May 16, 



Mercury and Jupiter together (one revolution) . 





O 





Observed. 



Calculated 



rs P"f "\X7 pp n 

 JJCU w ecu 



and 



30 



— 5 '76 



— 3 22 



55 



30 



60 



J. O tJO 



— 7 -56 



53 



60 



90 



— 33 "26 



—11 72 



53 



90 



120 



—43 -66 



JL 'J XX. 



U 



120 



150 



— 37 -91 



K> t OX. 



— 1 91 



55 



150 



180 



— 27 - 22 



— 8 -71 



55 



180 



210 



—11 '24 



— 4 -84 



33 



210 „ 



240 



+ 10 78 



+ - 73 



35 



240 „ 



270 



+ 27-76 



+ 5 "45 



33 



270 „ 



300 



+ 37-35 



+ 8-33 



35 



300 „ 



330 



+ 35 -33 



+ 7-29 



55 



330 „ 



360 



+ 16 -62 



+ 2-41 



The results of Table XI are exhibited in Diagram II, in which fig. 7 

 gives the observed and the calculated sun-spot inequalities for the 

 period of Mercury, and fig. 9 the same for the period of Mercury and 

 Jupiter. 



15. If we now turn to declination-ranges we shall find that there 

 are greater oscillations or sub-periods in the value of these ranges 

 during times of maximum than during times of minimum sun-spots. 

 But on the other hand the increased value of such oscillations is by no 

 means so striking as in the case of sun-spots. Mr. Broun has already 

 made the remark that while there is an increase in the whole declina- 

 tion-range during times of maximum sun-spots, yet this increase is 

 not so marked as in the case of the spots themselves, inasmuch as we 

 have a considerable declination-range when there are no spots on the 

 sun. From what has now been said it would seem that a similar 

 remark applies to the oscillations or sub-periods .of declination-range, 

 which, while increasing from times of minimum to times of maximum 

 sun-spots, do not yet increase so strikingly as the oscillations or sub- 

 periods of the spots themselves. 



16. If we now treat the inequalities of magnetic declination that 

 appear to depend on the two most available planetary configurations 

 in the manner in which we have just treated sun-spot inequalities, we 

 might expect the observed magnetic inequalities corresponding to 

 times of maximum sun-spots to be greater than the calculated in- 

 equalities, but not to the same extent as in the case of sun-spots. 



Let us make use for this purpose of the records of the three Obser- 

 vatories, Kew, Prague, and Trevandrum. We cannot, however, take 

 absolutely the same epochs that we have taken for the sun, inasmuch as 

 for the first of these, March, 1835, there are no magnetic observations. 

 We may, however, take the other two epochs, January, 1847, No- 

 vember, 1858, and an additional one at October, 1870. Thus we shall 



