May lo, 1877J 



NA TURE 



positions of some one prominent 

 planet, that we at once expect a 

 similar result in the case of another 

 planet of nearly equal prominence, 

 and are thus led to use our idea as a 

 working hypothesis." 



Proceeding upon this principle, 

 these observers measured every sun- 

 spot recorded by Mr. Carrington from 

 the beginning of 1854 to the end of 

 1S60, as well as every one photo- 

 graphed at the Kew Observatory 

 from the beginning of 1S62 to the 

 beginning of 1867, and the results of 

 all these measurements are recorded 

 in Diagram c. 



In this diagram each curved line 

 is supposed to represent the be- 

 haviour, as regards size,of the various 

 groups of spots as they pass across 

 the disc of the sun by solar rotation 

 from left to right. If, for instance, 

 a spot were always to retain the same 

 magnitude, its path would be repre- 

 sented by a horizontalfline, but if it 

 were to become smaller at the middle 

 of its course than at either ex- 

 tremity, then we should have it re- 

 presented as in the first figure. Now, 

 from this diagram, we find that when- 

 ever either Venus or Mercury is be- 

 tween or nearly between our earth 

 and the centre of the sun, the sun- 

 spots behave as in the first figure ; 

 that is to say, as they are carried 

 round by rotation nearer to the 

 planet, they become less, and as they 

 are carried away from the planet they 

 become greater. Secondly, when 

 Venus or Mercury is at the extreme 

 right of the sun the spots diminish in 

 size all the way across. Thirdly, 

 when Venus or Mercuiy is on the 

 other side of the sun, exactly opposite 

 the earth, the spots have their maxi- 

 mum in the centre ; and, finally, if 

 Venus or Mercury be at the extreme 

 left, the spots augment in size all 

 the way across ; in fine, they are 

 always least in the immediate neigh- 

 bourhood of Venus or Mercury, and 

 greatest when that portion of the 

 sun to which they are attached 

 is carried by rotation to the posi- 

 tion farthest from the influential 

 planet. 



If there be any truth in this evi- 

 dence it would seem to follow as a 

 corollary that when two influential 

 planets are together on one side of 

 the sun, their peculiar spot-producing 

 action should be conspicuously great, 

 and hence there should be a greater 

 than usual amount of spots when 

 such conjunctions take place. 



On the other hand, when one in- 

 fluential planet is on one side of the 

 sun and another on the other side, 

 they might be supposed to counteract 

 each other, and hence the spotted 

 area would be conspicuously small. 

 In a memoir which will be found in 

 the Transactions of the Royal Society 

 for 1870 the Kew observers have 



