PREFACE. 



THE progress of astronomical discovery was never more rapid 

 than during the last fifteen years. Within this period, the 

 number of known members of the planetary system has been 

 more than doubled. A planet of vast dimensions has been 

 added to our system ; thirty-six new asteroids have been dis- 

 covered; four new satellites have been detected; and a new 

 ring has been added to Saturn. 



It is especially gratifying to note the progress which the 

 last few years have witnessed in the United States, both in the 

 facilities for observation, and in the number of active observers. 

 It is but twenty-five years since t the first telescope, exceeding 

 those of a portable size, was imported into the United States ; 

 and the introduction of meridional instruments of the larger 

 class is of still more recent date. Now we have one telescope 

 which acknowledges no superior ; and we have several which 

 would be esteemed worthy of a place in the finest observatories 

 of Europe. We have also numerous meridional instruments, of 

 dimensions adequate to be employed in original research. Our 

 own artists have entered successfully upon the manufacture of 

 refracting telescopes of the largest size, and have received the 

 highest commendation from some of the best judges in Europe. 

 These instruments have not remained wholly unemployed. At 

 the observatories of Washington and Cambridge, extensive cata- 



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