PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



Vol. XLIX January-June, 1910 No. 194 



PHOTOGRAPHIC OBSERVATIONS OF DANIEL'S COMET. 



(Plates I-XXV.) 

 By E. E. BARNARD. 

 (Read April 25, 1908.) 



It is such a long time since one has had the opportunity of 

 seeing a large comet that the sight of this beautiful object sus- 

 pended in the quiet summer morning skies with its slender graceful 

 tail streaming upwards into the night, was something long to hh 

 remembered. It was a very impressive picture and those who were 

 fortunate enough to see it at its best must have been struck with 

 its quiet and majestic beauty. This was specially the case for a 

 few mornings in the middle of August when the moon was absent, 

 and as late as the first week in September when, though very low 

 in the east and visible only for a few minutes before dawn killed 

 it, the tail could be traced for a distance of fifteen degrees or more. 



This comet was discovered by Mr. Zaccheus Daniel at Princeton, 

 N. J., on 1907, June 9. Though it proved to be one of the brightest 

 comets that have appeared in the past twenty-five years, it was in 

 some respects a disappointing object — disappointing only, however, 

 in the want of new phenomena. It was visible to the naked eye for 

 two full months. At one time its tail attained a length of twenty-five 

 degrees. Shortly after perihelion passage — when last seen in the 



