The Motion and Distribution of the Sun-spots 



81 



that the outer layers have a greater angular velocity than the lower seems to be 

 indicated by the observations of the faculse, which give a somewhat shorter rotation- 

 period than the spot-observations. The accuracy of these observations of the faculse 

 is, however, difficult to determine, averages only being given. Another fact, pointing 

 in the same direction, is, as we have seen on page 44, that a greater angular 

 velocity is obtained from larger tlian from smaller spots. Since it now seeuis very 

 probable that, upon an average, the larger spots occur at higher levels than the 

 smaller, it should also follow from this that the outer layers rotate faster than the 

 inner. This different velocity of rotation is still more evident from spectroscopic 

 observations, especially those made at the Solar Observatory, M o un t W ils on ^• 

 As is easily seen, this may be the cause of a small spot Ijeing more easily observed 

 on the eastern half of the sun than on the western. 



C. The Place of Origin of the Sun-spots. Discussion of the Opinion 

 of Stephani. 



Another problem nearly related to that of the distribution is the question of 

 the birthplace of the spots. Since this problem on account of the writings of 

 Stephani has recently begun to attract some attention I shall here give the result 

 of an examination, regarding this subject, of the Ledgers published in the Green- 

 wich Observations. 



Dr. Cabl, München, remarks that during the period 1859 — 1864 spots only 

 exceptionally arose on the side of the sun turned towards the earth. An examination 

 made by Stephani of solar photographs taken at the solar observatory in Cassel 

 from 1905 — 1910 gives the result that of the 246 larger spots observed only 20 arose 

 on this side of the sun. As far as I can find Stephani does not state, where he 

 places the limit between »large» and »small» spots. The ratio 20 : 246 seems, ho- 

 wever, rather strange. A result such as that of Stephani would obviously, if 

 proved correct, be of the greatest importance to our ideas of the sun-spots and 

 their origin. 



In order to find out the real facts of this case I have examined the first 

 and last observations of all spots observed from 1886 — 1909 at different 

 distances from the central meridian. I have distinguished between recurrent spots 

 and such spots as have only been observed in one rotation. The result is given in the 

 tables XXXIV — XXXVII. Further, a summary of these observations is given in table 



' Walter S. Adajis: Speetrograpiiie Observations of the Eotation of tlie Sun. Astrophysical 

 Journal, Vol. XXVI, 1907. 



— , Preliminary Note on the Rotation of the Sun as determined from the Disj)lacenients of 

 the Hydrogen Lines. Astrophysical Journal, Vol. XXVII, 1908. 



George E. Hale: Preliminary Note on the Rotation of the Sun as determined from the 

 Motions of the Hydrogen Flocculi. Astrophysical Journal, Vol. XXVH, 1908. 



Luuds Universitets Årsskrift. N. P. Afd. 2. Bd 10. 11 



