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CAKNEGIE INSTITUTION OF WASHINGTON. 



trogram taken with very low dispersion and without a slit on August 

 16 indicates a fairly strong continuous spectrum upon which bright 

 bands appear to be superposed. 



The discovery of tlds nova led to a careful reexamination of other 

 photographs of spiral nebulae. As a result two stars were found near 

 the center of the Andromeda Nebula which, in all probability, ai-e also 

 to be classed as novae . Fortunately an extended series of photographs 

 of this object taken in 1909 and 1910 was available. Both stars were 

 invisible on a negative of August 13, 1909; were faint on a plate of 

 September 12; became bright on September 15 and 16; then grew 

 fainter and were just visible on November 7. They were not seen 

 after that date. At maximum these stars were of about the sixteenth 

 magnitude. 



Mr. Shapley and Mr. Pease have each found one nova on our photo- 

 graphs of spirals, while Mrs. Isaac Roberts has found one on photo- 

 graphs taken by her late husband, and Dr. Curtis has found three on 

 photographs made with the Crossley reflector. The further investi- 

 gation of such objects will undoubtedly prove to be a matter of great 

 importance in the study of spiral nebulae. 



Mr. Pease obtained during the year 30 photographs of the follow- 

 ing nebulae and star clusters, with exposures ranging from 15 minutes 

 to 5 hours 30 minutes : 



The cluster photographs were mainly for the purpose of securing 

 star counts, while those of the nebulae were for classification and deter- 

 mination of type — whether spiral, gaseous, or planetary. Several visual 

 observations are included as well. 



A photogi-aph of N. G. C. 1555, Hind's Variable Nebula, taken on 

 November 27, 1916, when compared with earlier negatives, showed 

 marked changes of form in the nebula. The most important difference 

 was in that portion near the variable star T Tauri. 



