OF ARTS AND SCIENCES. 229 



photographic maps of the region explored, and these would be of 

 incalculable service iu the astronomy of the future. 



In the latter part of the paper alluded to above, I state the specu- 

 lative basis upon which I restricted the stellar region to be examined ; 

 also the fact that between November of 1877 and March of 1878 I 

 was engaged in a telescopic scrutiny of this region, employing the 

 twenty-six inch refractor of the Naval Observatory. For the purposes 

 contemplated, I had no hesitation in adopting the method of search 

 whereby I expected to detect the planet by the contrast of its disc 

 and light with the appearance of an average star of about the thir- 

 teenth magnitude. A power of six hundred diameters was often 

 employed, but the field of view of this eyepiece was so resti icted that 

 a power of four hundred diameters had to be used most of the time. 

 I say, too, that, " after the first few nights, I was surprised at the 

 readiness with which my eye detected any vaiiation from the average 

 appearance of a star of a given faint magnitude : as a consequence 

 whereof my observing-book contains a large stock of memoranda of 

 suspected objects. My general plan with these was to observe with 

 a sufficient degree of accuracy the position of all suspected objects. 

 On the succeeding night of observation they were re-observed ; and, 

 at an interval of several weeks thereafter, the observation was again 

 verified." Subjoined to the original observations are printed these 

 verifications in heavy-faced type. 



In conducting the search, the plans were several times varied in 

 slight detail, — generally because experience with the work enabled 

 me to make improvements in method. Usually I prei^ired eveiy few 

 days a new zone-chart of the region over which I was about to search ; 

 and these charts, while containing memoranda of all the instrumental 

 data which could be prepared beforehand, were likewise so adjusted with 

 reference to the opposition-time of the planet as to avoid, if possible, 

 its stationary point. The same thing, too, was kept in mind in select- 

 ing the times of subsequent observation. Notwithstanding this pre- 

 caution, however, it would be well if some observer who has a large 

 telescope should now re-examine the positions of these objects. 



Researches in faint nebulie and nebulous stars appearing likely to 

 constitute a separate and interesting branch of the astronomy of the 

 future, it has seemed to me that the astronomers engaged in this work 

 may like to make a careful examination of some of the stars entered 

 in my observing-book under the category of " suspected objects." The 

 method I adopted of insuring re-observation of these objects was by the 

 determination, not of their absolute, but oidy of their relative positions, 



