208 



CARNEGIE INSTITUTION OF WASHINGTON. 



appears close beside another group. These deserve careful study in 

 the future. 



Classifying the spots on the bipolar basis, and counting single spots 

 as though they were the preceding members of such groups, Mr. 

 Nicholson has tabulated their polarities as shown in the table. The 

 data include all spots whose polarities were observed during the years 

 1913 to 1916, inclusive. The term ''regular" as applied to the polarity 

 of spots or the direction of whirl in the overlying Ha flocculi indicate 

 that the observations thus designated are in harmony with the rule 

 given in the last report. 



It will be observed that in the case of spot polarities the number of 

 exceptions to the rule is small — 18 in a total of 459. Of these, 8 are 

 of the spot type classed by the Greenwich observers as "faint mark- 

 ings"; 3 of the remaining 10 were observed on one day only, without 

 check observations; and 1 was a complex group in which the largest 

 member was regular. The floccuU, however, are much less uniform 

 in behavior. The exceptional cases should prove of great interest. 



As stated last year, the polarities of the spots reversed at the spot 

 minimum, while the direction of the Ha flocculi showed no change. 

 An interesting case is afforded by a photograph in which two single 

 spots of the same polarity, widely separated on the solar surface, are 

 accompanied by Ha floccuH indicating opposite directions of whirl. 

 The sun-spot maximum has hardly yet been reached, but if any rever- 

 sal of polarities is to occur at that time, no indication of it has yet been 

 detected. 



"HYDROGEN BOMBS" NEAR SUN-SPOTS. 



Observations made in previous years on the great widening of Ha 

 in small eruptive regions in the penumbra, or at other points near 

 active sun-spots, have been frequently repeated. The regions in ques- 

 tion are very small, usually only a few seconds of arc in diameter. 

 The narrow bright wings of Ha corresponding to them frequently 

 extend several angstroms on either side, fading in intensity toward 

 their extremities. Mr. Ellerman has recently succeeded in making 

 some good photographs of these spectral phenomena, which are Yevy 

 short-lived. 



