December 11, 1885.] 



SCIENCE. 



519 



The Biela comet meteor-stream. 



The showers of meteors from this stream (see 

 Science, vi. 489 and 496) were observed not only- 

 very extensively on the night of Nov. 27, but also at 

 some places on nights preceding and following this ; 

 and a complete collection of all the observations 

 should be made in order to study the distribution of 

 matter in the stream. We should be glad to receive 

 from everywhere reports of observations of these 

 showers ; and they should give, as fully as may be, 

 the following data : 1°. The time the observations 

 commenced, whether in twilight or darkness, and 

 whether the shower seemed to be beginning or 

 already in full operation. 2°. The clearness of the 

 sky, and freedom from interference of trees, street- 

 lamps, etc. 3°. If a continuous count was kept, the 

 rate at which it proceeded (as illustrated on p. 490 of 

 last week's Science), the number of observers, and 

 how stationed. 4°. If no count was kept, then the 

 time of any marked variations in the density of the 

 shower. 6°. The time the observations ended, and 

 whether the shower appeared to be over ; and, if so, 

 whether any further watch was kept for a renewal 

 of it, and how long. 6°. The appearance of the me- 

 teors, especially the color of the brighter ones and of 

 their trains, if any ; also if any appeared to describe 

 curved paths. 7°. If the observer was reclining so 

 as to watch all round the radiant equally well, or, 

 if there was an observer for each quadrant, then 

 some approximate indication, if possible, of the rela- 

 tive density in each quadrant ; and, if this varied 

 decidedly, then the times of the variation. 



Probably few can give much information on the 

 last point, but it would be valuable in discussion of 

 local differences in the showers. There are some in- 

 dications of this at stations not many hundred miles 

 apart, which, if they are real, indicate a considerable 

 bunchiness in the meteor-stream within very moder- 

 ate distances. These will always be interesting 

 showers to observe, not only for their connection 

 with the lost comet, but also because they come into 

 our atmosphere with low velocities, nearlj'^ on the 

 Jollowing side of the earth, and hence are con- 

 veniently observed in the evening and with the 

 radiant near the zenith, — very rare characteristics 

 of weU-marked showers. 



Some features of the meteor-orbit may be of inter- 

 est. Assuming the elements which Santini computed 

 {Astr. nachr., L. 124) for the unobserved return of 

 the comet in 1859 as the latest computation of its 

 probable motion, they show that the orbit is an elon- 

 gated ellipse inclined about 12° to the earth's orbit, 

 with a perihelion distance of .87 (the earth's mean 

 distance being unity) and an aphelion distance of 

 6.21 (Jupiter's mean distance is 5.20), and that the 

 a.pheHon is only .92 from the plane of the ecliptic ; 

 thus making it highly probable that Jupiter pulled 

 the comet into the solar system originally, and show- 

 ing that it can still perturb its motion considerably. 

 The most interesting feature (the one which makes 

 the meteor-showers possible) is that, according to 

 Santini's elements for 1859, the radius-vector of the 

 comet at its descending node equals .992, while that 

 of the earth at this point is .986, — an approach within 

 .006, or about 550,000 miles. This small distance, 

 however, is liable to have been changed by several 

 times its whole amount by perturbations since then. 



At this node the velocity in the comet-orbit is 24.3 

 miles per second, while the earth's is 18.7 ; and as the 

 motion of the comet is direct, the inclination only 



12", and the angle between the radius-vector and the 

 normal of the comet-orbit only 18% the meteors enter 

 the earth's atmosphere from the apparent direction 

 of the radiant in Andromeda, with a velocity of only 

 9.8 miles per second, thus causing their sluggish 

 motion, which perhaps would be even more marked 

 were it not likely, that, on account of their slow 

 speed, they are consumed at a somewhat lower level 

 than the swift showe.s, and hence appear relatively 

 too fast from greater proximity. 



Of course, there can be no shower unless there are 

 meteorites scattered along that part of the orbit where 

 the earth reaches the node about Nov. 27. Santini's 

 elements make the passage through the node about 

 thirty days before that through perihelion, and give 

 the following series of times for the successive cross- 

 ings of the node, the period being 6.67 years.* The 

 next column gives the elapsed intervals from these 

 times till the nearest earth-crossing about Nov. 27. 



Date of comet's node- 



Distance of comet bevond 



passage. 



node Nov. 27. 



1859.31 (April 23) 

 1865.98 (Dec. 24) 



—5 months. 



-1 



1872.65 (Aug. 25) 



-f3 " 



1879.32 (April 27) 



-5 " 



1885.99 (Dee. 27) 



-1 



1H92.66 (Aug. 29) 



+3 " 



1899.33 (May 1) 



-5 



The only recently observed showers certainly 

 attached to this stream, so far as known to the 

 writer, are those of 1872, when the comet was 

 already three months past the crossing, and the one 

 just happened, when, according to the same elements, 

 the comet should not have crossed till a month after- 

 wards. There appears to have been no well-marked 

 shower observed in 1865, when, with imperturbed 

 elements, the circumstances should have been almost 

 the same as this year; and the difference is, no doubt, 

 due to the increased diffusion of the stream and the 

 perturbations since 1859. The phenomena of 1892, 

 as compared with those of 1872, will furnish some 

 evidence on this point ; but, as the perturbations of 

 this stream are pretty large, the above times may 

 very likely be wrong by some months at the end of 

 the century. 



This is by far the most mteresting meteor-stream 

 we have to deal with as yet, and the study of its 

 special perturbations would seem to be well worth 

 making. After the passage of the double comet in 

 1852, the Academic des sciences de St. Petersbourg 

 offered a prize {Astr. nachr., xxxviii. 95) for a full 

 discussion of the whole theory of the comet from its 

 discovery in 1826 to its expected re-appearance in 

 1859 ; but no one seems to have undertaken the 

 work at that time. Perhaps its discussion at this 

 day, extended to its perturbations as a diffusing 

 meteor-stream, would be worthy of a prize. 



H. M. Paul. 



Washington, Dec. 5. 



The Biela meteors. 



On the evening of Friday, Nov. 27, at 6.15, I ob- 

 served a meteoric shower of considerable proportion. 

 In taking a casual glance at the heavens after tea, 

 my attention was at once attracted by several meteors, 

 which followed in such rapid succession that I was 

 able to count twenty in less than five minutes. They 

 appeared all over the heavens, and, among the great 

 number observed during less than half an hour, the 

 radiant point of but one was other than in the con- 



