188 



CARNEGIE INSTITUTION OF WASHINGTON. 



In the last annual report attention was called to a high-latitude spot which 

 was considered as a possible forerunner of the next sun-spot cycle. Three 

 more high-latitude spots have since been observed, one in September 1922, 

 one in June 1923, and one in July 1923. The September spot was at 29° north 

 latitude and was of positive polarity. The flocculi were of such a nature 

 as to make it uncertain whether it was a preceding or a following spot. The 

 spot of June 1923 was also at 29° N. and of positive polarity. This spot, 

 however, was in the following part of the surrounding faculse and seems to 

 have been a following spot. In that case its polarity was contrary to the 

 regular following spots of the waning cycle. The July spot was at 26° S. and 

 of negative polarity. This was also a following spot and therefore also oppo- 

 site in polarity to the regular southern spots. Both of these last spots were 

 observed only near the limb, where magnetic observations are difficult. The 

 question of the reversal of polarities at the minimum is therefore still some- 

 what uncertain. It seems probable that the spots of the new cycle will be 

 reversed in polarity, but this question will not be settled definitely until some 

 bipolar groups have been observed.^ 



All sun-spots observed throughout the year have been classified according 

 to the character of their magnetic fields. The results have been printed 

 every two months in the Publications of the Astronomical Society of the 

 Pacific. Miss Mayberry has assisted in the preparation of these records. 



For purposes of reproduction, Mr. Ridgway has continued the preparation 

 of a large number of diagrams taken from the records made with the 150-foot 

 tower telescope, showing the positions and magnetic polarities of sun-spots. 

 It is believed that a satisfactory method of publication has been secured 

 in this way. Mr. Ridgway has also made 15 drawings in great detail of 

 sun-spot groups and several drawings based on enlargements of hydrogen 

 spectroheliograms. 



INVISIBLE SUN-SPOTS. 



Observations of invisible sun-spots by means of their weak magnetic 



fields have been continued in the manner outlined in the last annual report. 



Only three such spots have been located during the year. The small number 



of such spots is due no doubt to the general low spot activity of the past year. 



HYDROGEN ABSORPTION MARKINGS. 



At the request of Professor Turner, of Oxford, measures have been made 

 by Miss Ware of the positions and areas of the hydrogen-absorption mark- 

 ings on all Ha spectroheliograms during the period from March to October 

 1922. 



1 Subsequent observations of bipolar groups completely confirm the general reversal of the 

 polarity at minimum described by Hale, Ellerman, Nicholson, and Joy in Mount Wilson Con- 

 tribution, No. 165. 



