106 



KNOWLEDGE. 



[July 1, 1898. 



NOTES ON COMETS AND METEORS. 



By W. F. Denning, f.r.a.s. 



Encke's Comet. — This comet will be comparatively near 

 the earth, but quite invisible to observers in this country. 

 Early in July moonlight will prevent observation, and at 

 the middle of the month the comet will have reached a 

 southern declination of nearly fifty degrees. 



Wolf's Comet. — The brightness of this object is slowly 

 increasing. It is situated in Taurus, and moving eastwards 

 at the rate of about forty minutes of arc per day. In the 

 Obscriatoni for May, Mr. Crommelin points out that the 

 comet will be only twenty-seven minutes of arc distant 

 from Mars on July 18th. 



TnnpeVs Comet (LS(i7, 11.). — Gautier computes that the 

 perihelion passage will occur on October 4th, but the 

 prospect of redetecting the comet is a slender one, on 

 account of its great distance. It has not been observed 

 since 1879, and the comet's orbit appears to have suffered 

 considerable disturbance in the interim, from the action 

 of Jupiter. 



Pcrrine's Comet (Marc/i ir/f/i).— Rapidly increasing dis- 

 tance from the earth will probably soon render this object 

 a difficult one. In regard to its position, it is, however, 

 favourably placed for telescopic observation, as it is 

 traversing the northern borders of Auriga, and remains 

 visible during the whole night. Mr. Perrine, from observa- 

 tions at the Lick Observatory, Mount Hamilton, on March 

 19th, April 8th and 28th, has computed elliptical elements 

 for this comet. He finds the period three hundred and 

 five years, and points out that there are some suggestive 

 orbital resemblances between the comet and those of 1684 

 and 1785, I. His conclusion is that these several bodies 

 probably belong to the same family, but do not represent 

 an identical object. 



The following are ephemerides : — 



Cometary Discovery. — It is a little remarkable that during 

 the last eighteen months only two new comets have been 

 discovered. Several periodical comets have been redetected, 

 but these objects being well-assured members of the solar 

 system their orbits and positions were known, and re- 

 observations of this character, though important in their 



way, cannot be considered in the light of new discoveries. 

 The apparent rarity in the recent visits of unknown comets 

 is probably to be attributed, not altogether to a real scarcity 

 of these bodies, but to the fact that they have not been 

 thoroughly searched for by a suilicient number of observers. 

 There is no doubt that many small comets come to perihelion 

 and pass beyond the limits of visibility without being de- 

 tected. This is evident from the fact that some of these 

 bodies have only been first discerned long after perihelion, 

 and when near the vanishing point, owing to their great 

 distance from the earth. The best period for efifecting 

 cometary discoveries is in July and August, and it is to be 

 hoped that more observers will apply themselves to this 

 work, so that comparatively few of these interesting objects 

 may be permitted to elude suitable record. 



April Meteors. — Mr. E. R. I)lakeley, at Dewsbury, ob- 

 served four Lyrids on the night of April 19th, and the 

 paths indicated a radiant at 268^ + 36°, which is nearly . 

 identical with his position for the same shower on 1895, 

 April 19th, viz., at 269° + 37° (nine meteors). These 

 positions for April 19th, when compared with Mr. W. E. 

 Besley's, obtained on 189H, April 21st-22nd, at 273' + 33 , 

 strengthen the idea of a shifting radiant, in accordance 

 with similar observations at Bristol in 1885 and 1887. 



The comparison of various lists of paths by Prof. A. S. 

 Herschel at Slough, Mr. Besley of Westminster, Mr. A. 

 King at Leicester, and myself at Bristol, has proved that 

 nine meteors, recorded during the April period, were observed 

 at two stations ; and I have computed their real paths as 

 follow : — 



The average heights were 68-8 miles at first appearance, 

 and 57'1 at disappearance. These extremes are less than 

 that usually found, but the difference is readily explained 

 by the low altitudes of the majority of the radiants, and 

 the nearly level flights of the meteors directed from them. 



July Perseiih. — The well-known shower of Perseids 

 commences at about the middle of July, but the exact date 

 has not yet been ascertained. Its radiant point on 1887, 

 July 19th, was definitely observed at 19" -t- 51°, and this 

 represents the earliest position hitherto determined. There 

 will be little moonlight to interfere with observation this 

 year between July 12th and 80th. The radiant moves 

 to the east-north-east, and its position on successive nights 

 in July, as determined from observations at Bristol during 

 the last thirty years, is as follows : — 



It is to be hoped that clear weather will enable the 



