ASTRONOMICAL OBSERVATORIES. 213 



wich and Hudson ; on 107 nights it was observed both at 

 Edinburg and Hudson ; on 95 nights at Cambridge (Eng- 

 land) and Hudson ; on 88 nights at Hamburg and Hudson ; 

 and on 40 nights at Oxford and Hudson. The discussion 

 of all these observations, the results of which are pub- 

 lished in Gould's Astronomical Journal, has furnished 

 the longitude of Hudson from Greenwich with a pre- 

 cision such as has been attained at but few other places 

 in the United States. 



In the summer of 1849, the observatory at Hudson 

 was compared with that at Philadelphia by means of the 

 electric telegraph, numerous signals having been trans- 

 mitted to and fro on four different nights, and the differ- 

 ence of longitude between these places has thus been 

 settled within a small fraction of a second. The accurate 

 determination of the geographical position of a single 

 such place in a new State, affords a standard of reference 

 by which a large surrounding territory is tolerably well 

 located through the medium of the local surveys. 



PHILADELPHIA HIGH-SCHOOL OBSERVATORY. 



The High-School observatory at Philadelphia was 

 erected at about the same time with that of "Western 

 Reserve College, but the instruments were not received 

 until the autumn of 1840. In the year 1837, a com- 

 mittee was appointed by the Board of Controllers of 

 Public Schools on the subject of establishing a Central 

 High-School in Philadelphia. At one of the meetings 

 of the committee, Mr. George M. Justice proposed the 



