222 



NATURE 



[January 4, 1900 



LETTERS TO THE EDITOR. 

 ([ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. ^ 



Contemporary Meteor-Showers of the Leonid and 

 Bielid Meteor-Periods. 



Part I. — Co- Leonid Showers. 

 As a large proportion of the November shooting-stars ob- 

 served and mapped in 1899 on and near the two chief shower- 

 nights, of November 14th and 15th, were «o«-Z£w;/a? meteors 

 •emanating from various contemporaneous centres of much less 

 •conspicuous star-showers of that month, than the eagerly ex- 

 pected but unfortunately not witnessed great spectacle of the 

 Leonids themselves, it may furnish a useful clue to some of the 

 foreign-lookiiig or unconforniable meteors' sources of which 

 several bright examples were no doubt mapped by observers in 

 the many able watches kept for the recently expected shower, 

 to mention some radiant-points which were noticed here to be 

 tparticularly active in about twelve hours of tolerably productive 

 meteor- watching, lasting one or two, to three hours, on each 

 flight of November ^th, 8th, loth, 12th and 13th, in clear dark 

 sky, before the moon had acquired sufficient strength to hide 

 the smaller meteors. Mr. Denning also watched for about 

 four hours on the nights of the loth, nth and 13th, seeing 

 four Leonids and twenty-four other meteors; and among nine 

 •tinconformable ones of which he sent me path-positions, three 

 -accorded in direction with radiant-points of my present list, and 

 one of these, on November loth, as well as a second meteor on 

 that night, was simultaneously mapped here, enabling real 

 paths of these two meteors to be concluded from the observations, 

 •as represented in this Table. 



bright Leonid, at I3h. 33m., ^ seen here in the half-hour till 

 2h. a.m. on the morning of November 15th, when the sky for a 

 short while was clear before thick fog and clouds intercepted all 

 view of the sky for the rest of that night and through all the 

 night of the 15th, with only a very partial break's exception for 

 an hour preceding daybreak on the morning of the i6th, when 

 nothing meteoric was seen, was the only view that I could 

 here obtain of any well marked phase of brightness or abund- 

 ance which the shower was expected to display, and which it 

 did actually display with some small intensity elsewhere, on its 

 two chief predicted nights. 



While no rapid rate of appearance of the Leonids was yet 

 noted here in the clear half-hour till 2h. a.m. on November 

 15th, I have learned from my brother. Sir W. J. Herschel, 

 that at Littlemore, near Oxford, he observed, with a small 

 party of watchers, quite an abundance of Leonids on that 

 morning, in clear sky, between ih. 15m. and 6h. 15m. a.m. 

 The total list recorded there in those five hours was 62 I^eonids 

 and 40 non-Leonids or ordinary meteors. To the number of 

 the Leonids, besides, should be added six or eight not charted, 

 from their coming too rapidly in one or two minutes at 5h. 25m., 

 and in five minutes after the appearance, at 5h. 40m. a.m., of 

 the brightest meteor of this watch, which will be referred to 

 more particularly below. Including those additions, the numbers 

 of Leonids noted in the successive hours before, and half-hours 

 after moon-set at i6h. 50m., were 



Hours ending at 



Numbers of Leonids 

 And Hourly rates.. 



Half-hours ending at 

 Number of Leonids 

 And Hourly rates.. 



I4h. 50m. 

 6 

 6 



t5h. 50m. i6h. 50m. 



i7h. 



[7h. 50m. 

 25 

 50 



i8h. 15m. (25m.) 

 7 (in. 25m.) 

 17 



The sky was generally clear, and extremely clear in the one 

 dark hour after moon-set. The hourly rates then show a 



Table I. — Real Paths of an e-Taurid, and of an i-Aurigid Shooting-star, doubly observed at Bristol and Slough, on November \oth 



1899- 



The first true Leonid seen here appeared at the close of a 

 short very clouded watch of 30m., at 5h. 59m. a.m., on November 

 13th ; at least as bright as Sirius, since it shone through clouds 

 which hid all stars except those of Leo's Sickle, from which its 

 course was directed. ^ In the earlier part, however, of that 

 night, and during all the preceding night of November nth, 

 the sky here had been completely overcast ; but Mr. Denning 

 saw. two small Leonids and three other meteors in 35m., at 

 Bristol, after I4h. 50m. on the latter night. Two third magni- 

 tude Leonids were seen here on the following morning of 

 November 14th, among four meteors mapped in a nearly clear 

 hour after 4h, a.m., and Mr. Denning noted a small Leonid 

 Avith two other meteors in about 20m., on that morning, after 

 5h. a.m. ; but the few tracks seen till then showed no great 

 activity yet of the looked for meteoric exhibition. A single 



1 This path was approximately from 99°, -f- 19° to 83°, + 15' ; about 15° in 

 g second. 



NO. 1575, VOL. 61] 



sudden increase ; but a very sudden rise occurred also in the 

 second half of that dark hour (from 28 to 50 Leonids per hour, 

 very soon arrested then by gradually increasing daylight), much 

 too abrupt and sudden an increase, it seems obvious, to be at 

 all possibly ascribed to fading lunar twilight. These observed 

 rates in the moonless sky seem thus pretty certainly to show 

 that a maximum of the meteor-stream was either fast approach- 

 ing and very near and imminent, or may perhaps even have 

 been just attained, when a close was put by daylight to my 

 brother's good view of the shower and to his carefully recorded 

 notes of this Leonid display's appearance. The proportion of 

 the number of Leonids to that of ordinary shooting-stars seen 

 in the watch at Littlemore, 6 or 7 : 4, nearly resembles, al- 

 though it did not quite attain the proportions noted at Romsey, 

 Hants, and at the University of Pennsylvania, U.S., on the 



1 This ist magnitude Leonid's path was from 113°, + 37° to 93°, -t- 39J ; 

 15° in S second, leaving a greenish-white streak all the way for about 2 

 seconds. 



