Kirkwoorl.] J-^^ [Api-il2, 



The interval between these epochs was 174. "IDS. Hence if these con- 

 junctions occurred on the solar meridian M, the sun, during the interval, 

 must have performed 7.047 i-evolutions. Now, 



174.d95 



-^ -^- = 24. d 826, 

 7.047 



the same value of the sun's period of rotation as was found in (6). The 



harmony of these results affords a striking confirmation of the proposed 



hypothesis. 



(19.) We have given a very imperfect discussion of the spot-cycles due 

 to the disturbing effect of Mercury, Venus, and the earth. These results 

 must be materially modified by Jupiter, whose disturbing influence has 

 not yet been considered. It is not too much to hope that by means of a 

 more exact analysis, in which the action of each of the planets, Mercury, 

 Venus, the earth, and Jupiter shall be taken into account, the condition 

 of the sun's surface may be predicted with as much certainty as the 

 ebbing and flowing of the tides at any particular locality on the surface 

 of our planet. 



(20.) An easy calculation will show that the greatest tide produced in 

 the sun's photosphere by any single planet must be less thanan inch in 

 height. The actual disturbance, therefore, is certainly much greater 

 than might reasonably have been expected from a cause apparently so 

 insignificant. It is conceivable, however, that the physical constitution 

 of the fluids forming the luminous surface may be such that a very slight 

 impulse may be sufficient to create a rupture, and thus occasion the phe- 

 nomena observed. 



(21.) The foregoing discussion justifies, we think, the following con- 

 clusions : 



1 . A connection between the behaviour of sun-spots and the configura- 

 tions of certain planets has been placed beyond reasonable doubt. 



2. The theory, however, of spot formation by planetary influence is 

 encumbered with anomalies and even inconsistencies, unless we admit 

 the co-operation of a modifying cause. 



3. The hypothesis that a particular part of the solar surface is more 

 susceptible than others to planetary disturbance is rendered probable by 

 the observations of different astronomers. 



4. The 11 -year cycle of spot-variation is mainly dejjendent on the 

 influence of Mercury. 



5. The marked irregularity of this period from 1822 to 1867, is in a 

 great measure due to the disturbing action of Venus. 



6. Wolf's .56-year cycle is determined by the joint action of Mercury 

 and the earth. And, 



Finally, ilie hypothesis proposed accounts, as toe have seen, for all the loell 

 defined cycles of spot-variations. 



Bloomingtotst, Indiana, March 15th, 1869. 



