380 SCIENTIFIC RECORD FOR 1885. 



"Thf synchronic lines are limited and intersected by the syndynames 

 of the edges of the tail. In the case of the Donati comet, Norton found 

 these lines to be nearly straight, passing near the nucleus. According 

 to Bredichin, the synchrones are rather circles of great radius, the ra- 

 dius for each comet increasing and diminishing with the radius vector. 

 When the emission of matter is intermittent, the synchronic circles 

 signalize the maxima by clear bands converging toward the nucleus. 

 The clear bands are reallj' hollow conoids, more or less flattened in the 

 direction of the plane of the orbit. 



" In the two memoirs before us, which are taken from the Annals of the 

 Moscow Observatory, M. Bredichin successfully applies his theory to dif- 

 ferent comets, of which we possess sufficiently accurate drawings, and 

 especially to the comet of 1744 and to the Pons-Brooks comet (1884). 

 They also contain a reproduction of the refutation of the criticisms of 

 M. Marcuse." (Radau, Bull. Astron., September, 1885.) 



Computation of comet orbits. — In the twentieth volume of the Viertel- 

 jilhrsschrift der Astronomischen Gesellschaft (pp. 287-312) will be found 

 in full Professor Weiss's exceedingly interesting report on the j^resent 

 state of the computations of the orbits of comets, presented at the meet- 

 ing of the Gesellschaft on the 19th of August, 1885. Nature contains 

 the following report of this communication : 



"Of the twelve ijeriodical comets returned at different times to their 

 perihelion, eight had again been regularly determined by the same cal- 

 culators. Of the remaining four, three were removed from our present 

 care : Biela's, which, as was known, had been lost to observation, and the 

 comets of Halley and Pons-Brooks, whose next perihelion lay too remote 

 in the future. There was consequently but one periodical comet (Bror- 

 sen's) to be taken account of. As to the remaining non returning comets, 

 of the 168 which had appeared in this century, forty-one were to be re- 

 garded as settled ; twenty-three had their orbits pretty well determined. 

 In the case of fifty-eight comets a new calculation of the orbit was desir- 

 able for various reasons, and in all forty-six had yet to be calculated de- 

 finitely. There was, therefore, a wide field of labor open. Professor 

 Weiss accordingly sought to commend to the society the establishment 

 of a common calculation bureau on the settlement of the questions at 

 issue, while the exact detailed treatment of a particular comet should 

 in future, as hitherto, be left to the initiative of a single calculator. In 

 the discussion following this address, Staatsrath Struve argued against 

 the founding of such a bureau on the ground that the comets were of 

 too peculiar a nature to accommodate themselves to the methodic treat- 

 ment of a calculation bureau." 



HoletscUck : Uber die Bahneines Kometen, der - - - nicht aus den Son- 

 nenstrahlen lieraustreten Jcann Wiener Sitzungsberichte, December, 1883, 

 (88: 1099-1162.)— It will be remembered that at the time of the total 

 eclipseof May 17, 1882, the French, English, and Italian astronomers who 

 met at Sohag, Egypt, observed the presenge of a comet mM^ the sun ; 



