202 ASTRONOMY. 



eye. " Prof. Winnecke finds that this comet may be identical with 

 the comet of 1382, 1444, and 1569, as well as that of 1506, and he is led 

 to suggest a period of sixty-two and one-third years as probable." 



The spectrum of this comet was observed by Konkoly, Backhouse, 

 and YoiTNG. It gives four bright lines, whose wave-lengths are, re- 

 spectively, 5,609, 5,492, 5,169, and 4,859 tenth-meters. The spectrum, 

 though faint, was continuous. 



October 7, 11, and 12, the spectrum was examined at Greenwich, and 

 was found to consist of the three usual cometary bands, the brightest 

 comparing well with that of alcohol vapor and that of the Bunsen-burner 

 flame. 



Comet E was discovered by Lewis Swift, of Warner Observatory, 

 Eochester, 1^. Y., October 10. It reached its maximum brightness ISTo- 

 vember 16 ; presented an ill-detined disk several minutes in diameter. 

 The i^articular feature of interest attending this telescopic comet is that 

 it is identical with comet III of 1869. 



Prof. FmsBY, of the United States Xaval Observatory, has also com- 

 puted the elements of this comet from observations by the Washington 

 transit circle. The perihelion distance of the comet appears to be a 

 little greater than that of the earth, and its aphelion is just beyond 

 Jupiter's orbit. These planets may greatly disturb its path in the 

 future. Prof. Frisby makes its i)eriod about fi\'e and one-half years. 



Comet F was a small bright telescopic object, one minute in diameter, 

 with a distinct central condensation. It was discovered by Dr. Pechule 

 at Copenhagen ; elements were computed by Dr. J. IIoletschek. 



Prof. Young observed this comet December 18, 19, and 22, and saw 

 two faint tails. One direct, as usual, away from the Sun, in nearly 

 the opposite direction, and the other roughly toward the Sun, though 

 deflected some degrees to the north. The two streamers made an angle 

 of 150<^ with each other. "Each was about thirty minutes long on the 

 ISth, and neither was seen after the 22d." 



The three periodic comets whose orbits have been the most carefully 

 examined are Encke's, Winnecke's, and Faye's. Their least distances 

 from the Sun are -^o, ^0% fn 0? of the Earth's distance, respectively. 

 It is well known that Encke's original researches indicated the exist- 

 ence of a resisting medium in space which, by opposing the motion of the 

 comet through it, gradually shortened its period of revolution. All of 

 Encke's comjoutations were repeated by Dr. von Asten, and his gen- 

 eral results confirmed. Dr. Mollee, of Lund, executed a like work for 

 Faye's comet, and found no such change in its period and the conclu- 

 sion was that, granting the existence of a resisting medium, it did not 

 extend so far as one and a half times the earth's mean distance. Dr. 

 Oppolzer has just concluded a similar investigation for Winnecke's 

 comet. He finds that its motion is altered in the same way as that of 

 Encke's comet, and the value of the resisting force is found to be almost 



