ASTRONOMY. 



By Prof. Edward S. Holden. 



INTRODUCTION. 



As the space available for tbe record of astronomical progress is com- 

 paratively small, the accounts here given must necessarily be the barest 

 summaries, whose chief end is to call attention to work which has been 

 done, in order that a reference may be made to more extended papers if 

 desired. At the same time it is clearly imi)ossible to give a specific ref- 

 erence to each of the papers consulted. 



For such bibliographic information the reader is once for all referred 

 to Darboux et HouiiiL's BuUetin des Sciences Mafhematupies et Astrono- 

 miques (monthly, Paris), to Nature (weekly, London), to Science (weekly, 

 New York), to the Observatory (monthly, London), and to other standard 

 journals. Free use has been made of reviews by writers in these and 

 other periodicals, particularly of the Record o/^sirowow?/, published by 

 Dr. J. L. *^. Dreyer in the Scientific Proceedings of the Eoyal Dublin 

 Society. 



NEBULA AND CLUSTECS. 



The Earl of Eosse has published Parts 1 and 2 (O^* to U^ R.A.) of 

 the " Observations of Nebulte and Clusters of Stars made with the six- 

 foot and three-foot reflectors at Birr Castle from the year 184:8 up to 

 about the year 1878" (Trans. R. Dublin Soc, Vol. II). This publication 

 (of which the third part, comprising the last ten hours of E.A., is in 

 the press) embodies all the work done on nebulte since the erection of 

 the six-foot telescope in 1845. In 1850 and 1861 abstracts of the observ- 

 ations on more interesting objects appeared in the Philosophical Trans- 

 actions, but all these abstracts are given over again in the new i^ublica- 

 tion, with the sole exception of the copperplate engravings, to which, 

 however, in all cases references are made in the text. Though even now 

 not every single note in the observing ledgers is published, nothing has 

 been sui>i)ressed which can be of the slightest value or imi)ortance. 

 The observations are given in the observer's own words, and the notes 

 which were added by Mr. Dreyer while arranging the work for pub- 

 lication are easily distinguished by being inclosed in brackets. These 

 notes deal especially with questions of identification, and nearly all the new 



nebulae which were found at Birr Castle in the course of years and which 



163 



