ABSTRACTS 



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 this issue. 



ASTRONOMY.— Publications of the U. S. Naval Observatory, second 

 series, 6: pp. LXXIX + 620, illustrated, 10 plates, 4°. 1911. 



When the Naval Observatory was moved in 1893 from the old site 

 to the new one on Georgetown Heights it was decided to discontinue the 

 practice of issuing an annual volume, and to publish volumes only occa- 

 sionally, these to contain, however, rather large pieces of work. Fol- 

 lowing this practice Volume VI includes all the Equatorial Observations 

 made during the period 1893-1907, inclusive, with the 26-inch and 12- 

 inch instruments, together with three appendices. The observations 

 of Eros for parallax, however, have already been published in Volume 

 III (second series). 



When the 26-inch was set up at the new site it was provided with a 

 mounting and accessories furnished by Warner and Swasey, of the same 

 general type as those of the large Lick and Yerkes telescopes. Of the 

 old Clark instrument there remained only the object glass in its cell, 

 the micrometers, the finders, and a few other small parts. 



The walls of the 26-inch Equatorial building are of brick faced with 

 rough white marble. In the plans for the new observatory, however, 

 it was not intended that the dome of this instrument should have a 

 masonry clrum. It was proposed to erect steel uprights to carry the 

 track for the dome, and have these uprights support a double wall of 

 sheet metal which could be easily ventilated. As constructed the L'o- 

 inch telescope is verj' conveniently handled, and is stable. In these 

 respects it excels, as far as can be learned, the large instruments made 

 abroad. 



As to some of the defects of the mounting, it may be noticed that 

 although the driving clock is big and heavy, and furnishes plenty «>t' 

 power to carry the instrument, it has always had a troublesome periodic 



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