56 



O. A. Åkesson 



from table XXV, which I have borrowed from the paper of Dyson and Maunder. 

 That any periodicity should exist in these variations does not seem probable. On 

 the contrary it seems as if the inclination had somewhat increased during the last 

 decennia. The sun being gaseous, several circumstances seem to indicate that one 

 cannot speak of a rotation axis in the same sense as in a rigid body. 



We will now proceed to investigate to what extent the material of observation 

 dealt with in this paper indicates any error in the position of the rotation axis of 

 the sun. To begin with we shall investigate whether any annual period does exist 

 in the motions of the spots. As the time for the appearance of the spots in our 

 card catalogue is stated in hundredths of a year, I have divided the material into 

 ten groups for each year. In doing this I have for the sake of comparison, taken 

 the two periods as well as the two hemispheres separately. In table XXVI the 



TABLE XXVII. 



Mean Values of the Motions in Latitude at different Times in the Year. 



Part 

 of the 



First Period (1886 — 1897) 



-0.003, 505 



+0.052 I 504 



+0 131 1 405 



+0.144 ! 506 



+0.112 i 561 

 +0.046 



+0.132 

 -0.025 



—0.012 



+0.( 



+0.116 



+0.138 



—0.002 



+0.076 



—0.036 



— O.OOi 



—0102 



—0.176 



Second Period (1898—1909) 



-0.180 



-O.o; 



-0.194 

 f 0.042 

 +0.022 

 f-0.045 

 -0.116 

 -0.005 



I +0,045 5 0 7 6 +0,009 3 7 21 | +0,079 1 37 99 +0,065 j| 167 43 + 0,046 +1,231 



--0.0I 



--0 096 

 - -0.065 

 - -0.006 

 - -0.154 



— 0.010 

 +0.126 



— 0.028 



1602 

 1681 

 1580 

 1567 

 1684 

 1840 

 1731 

 1580 

 1696 

 1782 



1886 — 1909 



+0.051 

 +0.063 

 +0.122 

 -1-0.109 

 -1-0.082 

 -j-0.049 

 -1-0.054 

 —0.001 

 +0.016 

 — 0.0G9 



result of this division is given. The computed means of the latitude motions are 

 brought together in table XXVII. 



During the period 1886 — 1897 an obvious periodicity appears, especially in the 

 northern hemisphere. On the other hand this periodicity does not seem to exist, at 

 least not so conspicuously, during the following period, which indicates that the axis 

 of the sun does not appear to occupy a fixed position. Still better does this 

 periodicity of the motions appear, when they are graphically represented. Although 

 it seems as if we could not expect to obtain any better determination of the 

 position of the sun's axis from the latitude motions, we will, however, on account 

 of these motions inquire further into this matter. 



We designate the values of the inclination and of the longitude of the ascending 

 node, employed in the computation of the heliographic co-ordinates, by / and L 



