84 IO\\^A ACADEMY OF SCIENCES. 



vicinity of the spot. On the 7th, however, a sudden out- 

 burst occurred; when the spectroscope was adjusted at 

 11:40 A. M., the entire region just preceding and for some 

 distance following, and also north and south of the spot 

 was greatly agitated, the Ha line being reversed and dis- 

 torted, small dark jets projecting from either side of the 

 line were noted in several places, and upon opening the 

 slit slightly, the flame and spike-like form of the disturb- 

 ance could be clearly seen, extending from the umbra to 

 the edge of the penumbra on the east edge; this phenom- 

 enon was particularly striking — the intensely bright scar- 

 let flame nearly in the center of the dark absorption band 

 of the spot spectrum being very interesting, the D3 line of 

 Helium was bright, and Dl and D2 and numerous other 

 lines widened. At 12:05 p. m. a small dark line, attached 

 to the Ha line, extended obliquely towards the red end of 

 the spectrum in the region just preceding the chief spot. 



Observations w^ere interrupted at 12:10 p. m. and could 

 not be resumed again until 1:40 p. m., but the entire dis- 

 turbance had then almost ceased, only a few slight reversals 

 being noted." 



The maximum length of the group was about 140,000 

 miles and the dimensions of the chief spot about 50,000 

 miles in diameter. This group returned by solar rotation 

 again in the closing days of September, and disappeared 

 after its third rotation at the west liuib on October 12th, sur- 

 rounded by extensive and brilliant faculse. 



1899. 



All solar phenomena declined rapidly during this year, 

 the average number of groups, spots and facula? being over 

 50 per cent less than in the preceding >ear. The total 

 number of days without spots amounted to 108 out of a 

 possible 259 days of observation, or nearly 42 per cent, 

 compared with 13 per cent for the year 1898. 



Spotless days occurred every month of the year, the 

 number being greatest in the month of August. The 



