August 9, 1883] 



NATURE 



35i 



THE SHOOT NG STARS OF THE JULY 

 METEORIC EPOCH 



QUETELET pointed out, many years ago, the period 

 July 26 — 30 as a meteoric epoch of considerable 

 intensity, and recent observations have fully confirmed 

 his opinion. There are two special showers contributing 

 to this result, mmely, the Aquariads and Perseids. The 

 latter merely represents the oncoming of the great August 

 display which culminates on the 10th and then rapidly 

 dies out. 



This year, on July 28th, the sky was very clear from 

 clouds (though a little haze prevailed), and a fairly good 

 opportunity was offered for witnessing these July meteors. 

 It was important that this should be done, because the 

 previous observations were not in satisfactory accordance. 

 Professor Herschel in 1S65, July 2Sth, had observed the 

 chief radiant near the bright star Fomalhaut, and in 18S1, 

 July 25 — }p, M. Cruls of the Imperial Observatory at Rio 

 Janeiro, found that the radiant point of more than 90 

 per cent, of the meteors observed during that period was 

 situated five degrees north of Fomalhaut In 1S80, July 

 ?8 — 30, Mr. E. F. Sawyer, of Cambridgeport, Mass., 

 found the major radiant to lie at a 330 3 , 8- 6", with minor 

 showers at 32S 3 — 15", and 34i°-io°. Colonel Tupman, 

 who watched these meteors with considerable success and 

 accuracy during the last few nights of July, 1870, de- 

 termined the focus of divergence as at 340 - 14", and the 

 writer from observations at Bristol in 187S and 1879, 

 corroborated this position, and found that in addition to 

 these Aquariads, there was a very rich contemporary 

 shower, directed from a point near the star cluster % 

 Perse i. 



Comparing the various observations to which we have 

 just briefly referred, it will be seen that considerable 

 doubt exists as to the exact centre of radiation of these 

 July meteors. Obviously the point is either in Aquarius 

 or further south in Piscis Australis, and near the con- 

 spicuous star Fomalhaut of that constellation. The 

 observations also suggest that there may be several 

 streams in marked activity at this epoch, and it was with 

 the object of obtaining further evidence towards the 

 settlement of this question, that I reobserved these 

 meteors on the night of July 28 last. 



I began watching the eastern heavens at 10.30, and at 

 10.36 a very fine meteor, as brilliant as Jupiter, appeared 

 near y Andromedae. It had a short path of only four 

 degrees, and left a vivid streak. The meteor was evi- 

 dently much foreshortened and close to its radiant point 

 slightly west of \ Persei, so that it was an early forerunner 

 of the Perseids. At 11.4 another fine meteor, of exactly- 

 similar type, was seen falling between a and ft Andromedae, 

 and at 1 1. 10 a third, considerably brighter and quite equal 

 to Venus, traversed a path of nearly thirty degrees 

 between Pegasus and Aquila, where it left a bright streak 

 of some twenty degrees for a few seconds. Several other 

 Perseids were observed later on, and the radiant point 

 was found to Heat 27° + 55°, which conforms fairly well 

 with the position I found for the same display in 1878 at 

 3 2 ° -+■ 53° (63 meteors). As to the expected shower of 

 Aquariads I was not disappointed, though during the 

 earlier part of the night only small ones were seen, and I 

 could not get the position of the radiant with the neces- 

 sary exactness. Between i3h. and I4h. however, I saw 

 eight Aquariads, and three of these were brilliant. At 

 13I1. 13m. one appeared just below /3 Andromeda?. It was 

 brighter than a first magnitude star. At 13I1. 37m. a fine 

 Aquariad, rivalling Jupiter, was seen in the west region of 

 Pisces, and at 13I1. 54m. another of the first magnitude 

 appeared in nearly the same place. They moved slowly 

 and left trains of sparks. 



During the 3! hours (ioih. to I4h.) that I continued to 

 watch I saw eighteen of these Aquariads, and by the inter- 

 section of the paths, found the radiant very sharply defined 



at 337 - 1 1', and close to the point I had determined in 

 1S78 and 1879. This shower was far superior to the 

 Perseids in the morning hours, and fully asserted its 

 claim to be considered as the special display of the 

 epoch. The meteors generally have long paths, as the 

 radiant point is not far above the horizon. In all I saw 

 48 meteors during the night, and of these no less than 28 

 belonged either to the Perseids or Aquariads. 



There can be no doubt that these July Perseids are 

 identical with the celebrated shower of August 10, 

 though the radiant point is some 8 D west in July. 

 I have watched these Perseids very carefully from July 

 25 up to August 16 in several years, and traced the 

 gradual shifting of the radiant point. From my observa- 

 tions during the last week of July, 1878, I had supposed 

 these July Perseids to form a distinct shower to the 

 Perseids of August 10, but from observations obtained 

 on intermediate dates, i.e. on August 3, 4, and 5, 

 the connection of the two showers is most certainly 

 established, and the displacement of the radiant point 

 on each successive night can be clearly distinguished by 

 those who will mark the tracks of such meteors as appear 

 near this radiant from say July 25 to August 15. 



As to the Aquariads, I believe the maximum takes 

 place on July 27-2S, when they are undoubtedly more 

 numerous than the early Perseids. I feel certain that the 

 radiant point is near 8 Aquarii or at 339 1 - 13 3 . There is 

 another shower near Fomalhaut, which appears to have 

 developed remarkable energy in 1881 from M. Cruls' ob- 

 servations, and there are also other showers in Aquarius 

 at this special period, which have led to the difficulty in 

 determining the position of the major radiant. There is 

 certainly a very fine shower of meteors at the end of 

 July from a point a few degrees S.E. of (i Aquarii, which 

 has been observed as follows : — 



July 25-31 . 

 1870 July 28 

 1 880 July 28-30 



July 25-31 



... 324- 6 Schmidt. 



... 326- 13 Tupman. 



... 328- 15 Sawyer. 



... 324- 9 Denning. 



I gave some details of this particular stream, which, it 

 may be added, is one remarkable for its large meteors, 

 in the Monthly Notices of the Royal Astronomical Society 

 for November, 1881, p. 38. 



It now becomes important to watch for the annual 

 returns of these meteors of the July epoch at observa- 

 tories in the southern hemisphere, where they may be 

 more favourably observed than in high northern latitudes. 

 Obviously, a shower near Fomalhaut will be in a great 

 measure marred by the extremely low altitude of the 

 radiant, as that star never attains an altitude even of io° 

 in this country. At stations further south, the 

 shower of Aquariads appears to be one of great strength 

 and to form a display of first-class importance. Obser- 

 vations made in 1879 show a wide disparity in the 

 number of these meteors visible in different latitudes. 

 Mr. D. W. Barker, during a voyage from London to 

 Melbourne {Monthly Notices, Vol. XL., p. 364), in that 

 year observed meteors falling at the rate of 180 per hour 

 on July 2S and 120 per hour on July 29, between oh. and 

 4h. a.m. on the dates referred to. Yet, at Bristol on July 

 28 of the same year, the hourly number was only 23. 

 and on July 29, 11. , 



The further investigation of the July meteoric epoch 

 offers an attractive field to observers. Apart from the 

 rich shower of Aquariads there are the Perseids, equally 

 interesting from the fact that these early members of the 

 great shower prove it to be one of long duration, and to 

 have a radiant point which shifts its position amongst the 

 stars from night to night. These interesting details will 

 no doubt come under frequent observation in future 



years. 



W. F. Denning 



