438 



KNOWLEDGE. 



November, 1913. 



Double Stars and Clusters. — The tables of these referred to the corresponding month of last year, 

 given last year are again available, and readers are Variable Stars. 



Table 86. Non-Algol Stars. 



Principal Minima of /3 Lyrae Dec. 4 d l h e, 17 d ll h m, 30 d 9 h m. Period 12 d 21 h -8. 

 Algol minima Dec. 3 d 6 h 18 m e, 6 d 3 h 7 ra e, 15" 5 h 34™»j, 18 d 2 h 23 m m, 20' 11" ll m e, 23 d 8 h m e, 26 d 4 h 49 m e. Period 2 d 20 h -8. 



SOLAR DISTURBANCES DURING SEPTEMBER, 1913 



By FRANK C. DENNETT. 



September has yielded very little appearance of activity 

 upon the Sun to the ordinary telescopic observer, although to 

 the spectroscopist there does seem to be some increase. No 

 observations were made on two days during the month (1st 

 and 5th), spots were recorded on six days (6th to 10th and 

 16th), and faculae on nine others (3rd, 14th, and 24th till 30th). 

 On the remaining thirteen days the disc appeared clear. On 

 September 1st the Central Meridian was 37° 27' at noon. 



No. 11. — So late as 10 a.m. on September 6th the disc was 

 reported clear, but at 1.20 p.m. a small irregular penumbraless 

 spot was recorded. On the 7th it had four or five smaller 

 companions, some bridged over, hydrogen flocculi were lying 

 about the area, causing displacements of the C-line, first to 

 red and later to violet. On the 8th the leading spot had 

 increased somewhat, and a trailer spot with small companions 

 had developed. Prominences were seen in projection over 

 the group, as well as dark hydrogen flocculi. On the 9th only 

 some members of the leading group visible, edged with 

 brightness, and on the 10th, at 8 a.m., just one pore was left 



amidst the group of faculae which marked the area ; but it was 

 gone by midday. The group reached a length of 45,000 miles 

 on the 8th. The dark line of helium, D 3 , was traceable over 

 this disturbance on the 7th, 8th, and 10th. 



On the 16th, at 8 a.m., there appeared to be traces of pores 

 on several parts of the disc, the largest being in South latitude 

 some two days past the central meridian, and therefore near 

 longitude 227°. 



Faculae were seen near the eastern limb, well to the north, 

 on the 3rd ; on the 7th a small facula near longitude 258° 

 and 60° N. latitude ; on the 14th several bright flecks 

 appeared scattered over the disc. Faculic flecks were persist- 

 ently visible in the region within 20° of the north pole, records 

 being made on the 24th and 27th to 30th ; a faculic region 

 over, and just ahead of, the area of No. 11, within the eastern 

 limb, seen from the 25th until the 27th. 



The observers whose work has contributed to this note 

 have been Messrs. J. McHarg, A. A. Buss, C. Frooms, 

 E. E. Peacock, and the writer. 



DAY OF SEPTEMBER, 1913 



\o a jo 10 so so n 



SO 100 110 120 BO 140 ISO (0 170 180 190 ZM W 220 230 »0 250 260 270 280 290 500 310 320 330 340 350 360 



CORRESPONDENCE. 



LIGHTNING FLASHES. 

 To the Editors of " Knowledge." 



a most vigorous but short-lived thunderstorm developed some 

 distance to the north-west of Johannesburg. The flashes of 

 lightning, which were principally cloud-earth discharges, were 

 Sirs,— During the evening of Tuesday, December 5th, 1911, very brilliant, and followed one another at short intervals. I 



