E. ©. Pickering—New Planetary Nebule. 303 
Art. XXXIIL—WNew Planetary Nebule; by Epwarp C. 
PICKERING. 
seen to be a star when the telescope is gi oe The retina 
appears to be especially sensitive to rays of particular wave- 
lengths. The strain upon the eye and mind in examining so 
many objects, several a second, renders this work very fatigu- 
ing and I have found it best not to continue it for more than 
half an hour without an intermission, A count of the number 
of stars to be seen ata time in fields taken at random shows 
