Remarks on the Tails of Halley^s Comet. 325 



tails." I believe the one seen here and in England* was also called 

 a tail by an English astronomer. Six rays were seen in Germany 

 on the 13th, when the state of the sky was here unfavorable. The 

 sector of the 16th was here divisible into three. Three sectors were 

 seen at Paris on the 21st, when the comet itself was to us invisible. 

 But in all the published observations made at Paris, there is a close 

 correspondence with those made simultaneously here, and with some 

 not simultaneous. This is more than was to be expected, consider- 

 ing the difference of instruments. This correspondence will be seen 

 from the following extracts from the Annuaire. " 15th October, 

 1835, at 7 o'clock in the evening, the great telescope of the obser- 

 vatory of 'Paris, furnished with a great magnifying power, enabled 

 one to perceive in the circular nebulosity which is called the cheve- 

 lure, a little to the south of the point diametrically opposite the tail, 

 a sector, comprehended between two lines sensibly straight directed 

 toward the center of the nucleus. The light of this sector exceeded 

 remarkably that of all the rest of the nebulosity. Its two limiting 

 rays were distinctly defined." Their angle is not stated. The above 

 description as to form and brightness is applicable to the appearance 

 here on the 12th. The position, however, was different; and this 

 circumstance, if its identity could be established, would afford evi- 

 dence of a rotation in the comet. But the published data are not 

 sufficient. It may have been a different sector. "On the next day, 

 the 16th, after sunset, it was perceived that the sector of the 15th 

 had disappeared ; but in another part of the head, to the north, this 

 time, of the point diametrically opposite to the axis of the tail, there 

 was formed a new sector." It was considered a new one, " on account 

 of its situation, its truly extraordinary brilliancy, the perfect distinct- 

 ness of the rays by which it was bounded, and its great angular open- 

 ing, which exceeded 90°." A similar view was afforded by our tele- 

 scope, except that with it the sector of " about 90°" (which was 

 the angular opening that I had assigned to it,) was divisible into 

 three others, viz. two equal lateral ones and a more brilliant central 

 one embraced by the two former, as though a brilliant cone was sur- 

 rounded by,a conical brush of less brilliancy but still greatly exceed- 

 ing in brightness the rest of the nebulosity. Is it not probable that 

 with a telescope having a far greater aperture than ours, the brillian- 

 cy of the whole might appear so intense as to render the difference 

 in brilliancy between the lateral and middle parts less apparent ? 



* I do not know on what day. 



