May 31, 1883] 



NATURE 



!05 



THE TRUE ORBIT OF THE AURORAL 

 METEOROID OF NOVEMBER 17, 1882 



AFTER many fruitless efforts to conciliate the appa- 

 rently widely diverging data, given by the nume- 

 rous observations of this most interesting phenomenon ; 

 and after having been many times on the sime point 

 as Mr. H. D. Taylor (vol. xxvii. p. 434), who has 

 given the first approximate calculations of this orbit, 

 namely, " to give up the reconciling of such contradictory 

 evidence," I have devoted my Easter holidays to new 

 research on the true orbit. Besides the encouraging 

 letters received from so ne of the English observers, I 

 found still another motive in the observation of Mr. 

 Julius Dupire at Laon (France, /3 = 49/ 34'), who had the 

 kindness to give me ample information, for which I offer 

 him my sincere thanks, and in the communication of the 

 following citation, kindly given me by Prof. Ch. Mon- 

 tigny, of Brussels, taken Irom the Bulletin de P Obser- 



vatoire de Bruxelles, November 18, 1882 : "A 6h. 23m. 

 un enorme rayon d'un blanc vif s'dleVa a l'horizon 

 E.N.E. ; il traversa le ciel en passant le zenith et alia 

 s'dteindre a l'horizon O.S.O." A similar phenomenon 

 has been observed by Dr. F. Terby at Louvain. The 

 great attraction of the Laon observation consisted in the 

 fact that the meteor's apparent path was there seen at 

 the north side of the zenith, this being in harmony with 

 the Brussels zenith observation, and promising a good 

 determination of the sought orbit. 



In the first place I took the following apparent orbits 

 from the numerous given observations. They can cr 

 must be taken as great circles, and must, in this case, 

 fulfil the condition of intersecting one another in two 

 opposite points of the sphere. In fact their intersections 

 are contained within a small space and gave me an 

 approximate position to one of these two points, a = 70 30', 

 8 = -f- I4 C 30'. 



These five apparent orbits, the only ones given com- 

 pletely, are the following : — 



Place of obser- 

 vation. 



York, 

 $ = 53° 58'. 



Clifton (Bristol), 

 j8 = 51° 28'. 



Old Windsor, 

 = 5i°3°'- 



Utrecht, 

 = 52° 5'- 



Zonnemaire (near 

 Zierickzee), 

 = 5>°42'- 



Pages of 

 Nature, 

 vol. xxvii. 



87, 140, 434 



85 



87 



296 



296 



Data of observation. 



Deduced h irizontal 

 direction. 



Local time of max. 

 elevation. 



Observer. 



The centre was 6° or 7° 

 below the moon's centre 

 (given not directly after 

 observation) ; 30° eleva- 

 tion in meridian(probahly 

 a mistake or a printer's 

 error, being in contra- 

 diction with the other 

 data). 



S° from .Saturn, to the 

 right, in a line inclined 

 45 to the horizon. 



First seen a lit le S. of 

 Aldebaran ; moves across 

 the moon's disk. 



Aldebaran and two points 

 in the equator at 110° 

 and 290 R. A. 



Aldebaran and 8 Pegasi 

 (a Pegasi on p. 296 was 

 a printer's error). 



E. 20 N.-W. 



20°S. (nearly) ; 

 deduced by ihe 

 observer. 



61). 4 or 5m. 



H. D. Taylor. 



6h. 4m. 



6h. 6m. 



6I1. 24m. 



6h. 21m. 



A. M. Worth ington. 

 John L. Dobson. 

 Prof. J. A. C. Oudemans. 

 T. Zeeman. 



Tracing these five apparent orbits on a celestial globe 

 they gave the intersection point above mentioned. It is 

 clear that this point, joined with the eye of the observer, 

 gives the direction of the true path. This point lying 

 further, the globe being placed on the different latitudes 

 and hours, not far from the point E. 20° N. of the 

 eastern horizon (at Utrecht 7° above the horizon), it is 

 evident that the lines of intersection, formed by the plane 

 of the mean horizon with the planes of the apparent orbits 

 must be nearly parallel to this direction. That these 

 lines of intersection cannot be true parallels follows from 

 the observations of the four students at Cooper's Hill 

 (p. 97), from that of Mr. Joseph Clark at Street, com- 

 municated by Mr. J. E. Clark, at York ; and from that of 

 Mr. A. S. P. at Cambridge (p. 87), who saw the pheno- 

 menon disappear in the S.W., S.\V. and S.S.W. Further 

 the Revue Mensuelle of M. C. Flammarion (2 me Annee, 

 p. 72), containing a short report of Mr. Dupire's observa- 

 tion, mentioned above, gives also an observation made 

 at Ploermel (/3 = 47 5?', X 2 23' W. Greenwich), where 

 the phenomenon disappeared in the west. 



Now I have drawn a stereographic map on a large 

 scale, and brought the intersection of the vertical plane 

 through Brussels, with the bearing E. 20 N. It is clear 



that the true orbit must lie in the vertical plane. Further 

 I have constructed the angles formed by the planes of the 

 apparent orbits with the respective horizons, correcting, if 

 necessary, for the curvature of the earth, and after much 

 trouble found the following path, being a straight line 

 having the properties given in the table on p. 106, that 

 enables us at the same time to compare the results of my 

 construction with the data of the different observations 

 given in order from E. to W. 



I hope that the observers will be content with the de- 

 gree of harmony between their observations and my 

 results. I believe that a small change in the direction of 

 the orbit's plane will give still more harmony between 

 calculation and observation, but the orbit found satis- 

 fies the chief observed facts, and gives the greatest 

 divergence, where the observations have the smallest 

 sharpness. I believe I have proved by this research that 

 there existed, with the aurora of November 17, 1882, 

 cosmic dust, passing through the upper strata of our at- 

 mosphere with great velocity, and giving, according to 

 the most interesting observation of Mr. Rand Capron 

 (p. 84), " the usual green line " of the aurora spectrum. 

 Thus nature itself has been so kind as to give an experi- 

 ment that till now, and perhaps for ever, is beyond human 



