458 



NATURE 



{Sept. II, 1879 



from foreign observatories. The nights of August 9 and 

 II were partly clear, and a few observations were ob- 

 tained. Mr. H. Corder, in Esse.x, saw 166 meteors on 

 the nth, between 9.30 and 15.30, and found the radiant 

 point very distinct at 45° + 57°. On August 4 a few 

 meteors were seen from one of the earlier radiants at 

 33° + 5 1°» and on the 6th from another at 36" + 58°. On 

 the 9th he watched from gh. 30m. until i3h. seeing only 

 33 meteors (23 Pericids), but the moon was up and there 

 were a few clouds. On the loth it was cloudy except 

 between 12-12.30, but a few meteors were seen later, in 

 all 21, 18 being Perseids. The horary number cannot 

 have been much over 30. On the 12th in 2h. he recorded 

 22 meteors (14 Perseids). Two fine meteors were seen 

 on the loth, the first, at 12. 25, gave a vivid flash low 

 down in Cetus, but only the streak was well seen. It was 

 one of those instantaneous meteors often seen amongst 

 the Perseids. Another was noted earlier (at 10.30) in 

 Ursa = Sirius, and leaving a fine streak. 



At Welling, in Kent, 50 meteors were counted by two 

 observers from 10.15 to 11.15. 



At Debenham, Suffolk, on August 10, 12 meteors were 

 seen between 10.30 and 11. 5, but the sky was much 

 clouded. On the nth, 10 to 11.30, 95 were recorded by 

 one observer. These figures indicate a somewhat numerous 

 return of the Perseids on August 1 1. The radiant point 

 was deduced as at 46 J- + 5 7 J. 



At Blackheath, S.E., Major Tupman found the normal 

 radiant at 45° + 56^ on August 1 1, and describes the 

 Perseids as a poor display between 10.15 and 12. 



At Bristol, on August 9, 33 meteors were seen by the writer 

 between 9.30 and 12, but there was much interference from 

 clouds. On August 1 1 20 meteors were noted in the half- 

 hour preceding 10.10, and 15 of these were Perseids. 

 Radiant point fairly well defined at 46° -f- 58°. 



It will be seen that the four determinations of the radiant 

 here given almost coincide at 45^° + 57°, and prove the 

 meteors to have exhibited an exact and distinctly marked 

 centre of divergence this year. Mr. Greg's average posi- 

 tion for the Perseids, derived from a large number of 

 former observations, is at 44° + 56", and the writer found, 

 in 1874, 1876, and 1877, a sharply defined radiant at 

 43° + 58°, but has more recently detected the existence of 

 two other simultaneous showers from x and y Persei. 



Signor Denza reports {Gazetta Piemontese, August 27 

 and 28) that a total of 1,155 shooting stars were observed 

 on the nights of August 9-12 at seven Italian stations, 

 chiefly at Volpeglino, by Signor Maggi and his assistants. 

 The greatest number were recorded on August 11. The 

 Italian observers also succeeded in registering 295 meteors 

 on twelve nights in July. 



The apparent diffusion of the Perseid radiant point, often 

 noticed by observers, is explained by the activity of many 

 concomitant showers. Observations of the paths much 

 foreshortened and close to the centres upon which they 

 converge are the best to rely upon in getting accurate 

 radiants. The vast number of simultaneous or contem- 

 porary systems in operation is shown by a discussion of 

 a portion of the mass of observations which have been 

 collected on the night of August 10. There are certainly 

 more than 60 distinct meteor streams visible on that 

 single night alone, and evidence of many others whose 

 feebleness allows them to elude discovery. The extreme 

 tenuity of some showers is such that no indication of 

 their existence may be detected in a persistent watch of 

 several hours' duration. 



The true Perseids are characterised by the swiftness of 

 their flights (the theoretical parabolic velocity being 38 

 miles per second) and by the bright and often enduring 

 streaks left in their courses. They are sometimes very 

 brilliant, ending in green flashes of remarkable lustre, and 

 the luminous wands they leave behind guide the eye 

 unerringly back to the point of space whence they are 

 directed. They may be most favourably seen in the 



morning hours, when the radiant has attained consider- 

 able altitude ; and the observer should take up a position 

 commanding an uninterrupted view of the north-eastern 

 constellations. 



The limits of duration of this shower have not been 

 definitely ascertained, but very few Perseids are visible 

 before August 5 or after August 15. It is certain that they 

 open as early as August 5, because Heis, in 1864, saw a sta- 

 tionary meteor on that date, as brilliant as Venus, exactly in 

 the radiant point at 44° -f- 57°. None of the real Perseids 

 are visible as late as August 21, 22, or 23, for of many 

 shooting-stars seen on those dates this year, not one could 

 be certainly attributed to that stream. It was formerly 

 considered probable that the shower began at the end of 

 July, but from the paths of hundreds of meteors recorded 

 by the writer at Bristol during this epoch, there is little if 

 any indication of the true Perseid radiant point. There is, 

 however, a very rich display of swift streak-leaving 

 meteors from a point below x Persei, or more exactly at 

 32° + 53°, with which the old Perseids have been con- 

 founded, and given that shower an apparent duration far 

 beyond the actual limits. 



In addition to August 10 there are other nights in that 

 month when shooting-stars should be looked for and their 

 horary numbers and radiants ascertained. Large meteors 

 have been recorded in exceptional frequency on the 19th- 

 20th and 22nd, and a series of three fine nights, occurring 

 consecutively this year, on August 21, 22, and 23, enabled 

 the writer to obtain observations as follows : — 



Date, Time. 



1S79. h. m. h. m. 



Aug. 21 ... 9 30-13 30 



Duration, Meteors cn„ 



hours. seen. "' 



AC \ Clear ; stars very 



•4 - 68 brilliant. 



,, 22 ... 9 o-iS 15 ... 6i ... 70 ... Partly cloudy. 

 „ 23...9.S-IS o ... Sf ... 73 j Clear; cloudsat 



Aug. 21-23... 9 0-15 IS 



16 



Not many large meteors were observed, but three of 

 them were as bright as Jupiter. On the night of August 

 22 there was slight interruption from clouds, and the 

 watch sustained for 6^ hours under such conditions was 

 not equivalent to more than about 5 hours of clear sky. 

 Of the 211 meteors seen, no less than 52 belonged to a 

 splendidly well defined and rich shower of Draconids 

 from a point at 291° -f- 60°, which thus apparently consti- 

 tutes a special display at this epoch, and one of far more 

 than ordinary importance. On August 21, 2i of its 

 meteors were seen ; on August 22, n ; and on August 23, 

 20. They are slow-moving, bright meteors, sometimes 

 trained, and almost invariably with short paths. The 

 maximum occurred on August 21, when in | hour before 

 10.15, 9 °f ^^ meteors were traced, though, singularly 

 enough, during the next hour the radiant gave no visible 

 sign. It is not a new system, for the same shower has 

 been seen by many observers, and is No. 78 of Mr. 

 Greg's Catalogue of radiant points (1876), in which the 

 centre is given at 282 + 60 (12 obs.), and the duration 

 from June 28 to August 25 (?). Major Tupman detected 

 it in 1 87 1, on August 20-25, at 280"+ 58°, and Corder, in 

 1877, saw 1 1 meteors from 307° + 65°, on August 17, which 

 may have been another manifestation of the same stream. 

 In future years these Draconids should be anticipated as 

 a rich and interesting periodical display. Though none 

 of the true Perseids were risible on August 21-23 this 

 year, there was a moderately strong shower near a Persei, 

 at 46° + 47°, giving bright, swift meteors, with streaks, 

 and other radiant points were indicated in Perseus at 

 61°+ 50° and 62" + 35°, but no shower derived from the 

 211 meteors seen on August 21-23, would bear any com- 

 parison to that of the Draconids referred to. 



The night of August 24 was overcast, but on August 25, 

 before midnight, 14 meteors were seen through openings 

 in the storm-clouds. There were four Draconids, two of 



