ASTHONOMY. 3 



been photographed several times by Gould at Cordoba; and 

 Dr. Gould also reports that he has eight plates of Ma Argils 

 and surrounding stars, of which a very large number is se- 

 cured upon the photograph by an exposure of from eight to 

 ten minutes. 



Dr. Valentiner, at Mannheim, has begun the investigation 

 of several star clusters, and such investigations are to be 

 continued as a principal work of this observatory. 



At Kiel, Peters continues observations of nebula? for posi- 

 tion, which were undertaken at Altona. 



Dr. Schmidt, of Athens, has just published in the Astrono- 

 mische JVachrichten a suggestive paper on the connection of 

 the nebula h. 3770 with variable stars in the vicinity. His 

 facts seem to indicate a relation between them. 



M. Tempel, of Florence, sends to the Astronomische JVach- 

 richten, No. 2138, a long account of his observations of nebula? 

 at Florence, which are prosecuted under many difficulties, 

 and gives some account of the great variations which he has 

 found to exist between drawings of the same nebula by va- 

 rious observers. 



Professor Holden has a paper in Sillimaii's Journal on the 

 proper motion of the Trifid Nebula. 



From the older observations of the two Herschels it fol- 

 lows that 



1. From 1784, July 12, to 1833, the triple star Sh. 379 icas 

 centrally situated between the three nebulosities. 



Again, from the later observations of Mason, Herschel, 

 Lassell, Langley, Trouvelot, and Holden, it follows that 



2. From 1839 to 1877 the triple star was not centrally situ- 

 ated beticeen the three nebulosities, but involved in A. 



It is shown that each of these propositions rests on a firm 

 basis. Granted that 1 and 2 are correct, there are but three 

 ways to reconcile the opposing facts : 



a. The triple star has a large proper motion. 



b. The nebula has a large proper motion. 



c. The nebula is subject to decided changes of brilliancy. 

 The first point will be settled by meridian observations 



now in progress. The relative positions of the various stars 

 of the group seem to have been unchanged since 1839. If, 

 as is probable, the proper motion of the triple star is small, 

 there remain the two alternatives b and c to choose between. 



