ASTRONOMICAL OBSERVATORIES. 223 



vided with all the usual means of adjustment, together 

 with a vertical collimating eye-piece, and an illuminating 

 apparatus for dark field and bright lines. Professor 

 Bartlett, the director of the observatory, has suEjecited 

 this instrument to a severe trial, and finds the probable 

 error in the measurement of an angle of 60 to be but 

 0".22, exclusive of the error of reading. There is also a 

 sidereal clock in the same tower. 



A new refracting telescope, designed to take the place 

 of the Grubb telescope in the central tower of this ob- 

 servatory, has just been completed by Mr. Henry Fitz. 

 This telescope has a focal length of 14 feet, and an aper- 

 ture of nine and three fourths inches. It has seven neg- 

 ative and six positive eye-pieces, the highest magnifying 

 power being 1000. The circles are each 20 inches in 

 diameter, the hour circle reading to two seconds of time, 

 and the declination circle to 20 seconds of arc. The price 

 of this telescope was $5000. 



Professor Bartlett made a series of observations on the 

 great comet of 1843, which are published in the " Trans- 

 actions of the American Philosophical Society." He has 



also made numerous observations with the meridional in- 



. 



struments, which have not yet been published. 



NATIONAL OBSERVATORY AT "WASHINGTON 



Soon after the completion of the West Point observa- 

 tory, the National observatory at Washington was com- 

 menced. The origin of this establishment may be traced 

 to the wants of the naval service. In the year 1831, there 



