Order of the Starry Firmament. 77 



structed. Four observatories, completely fiirnished with In- 

 struments, have been founded in Russia within the last twen- 

 ty years. 



F, G. W. Struve, Director of the observatory at Dorpat, 

 an able and excellent astronomer, has turned to an impor- 

 tant account, the superiority of this new Instrument, m a 

 more extended and accurate examination of double stars 

 than has been effected by any preceding astronomer. The 

 following are extracts from an analysis of his report on this 

 subject by A. Gautier. 



The new measures executed in England and at Dorpat, 

 akeady surpass in precision those of the great astronomer 

 to whom we owe the discovery of Uranus, on account of the 

 perfection of micrometers. But the achromatic telescopes, 

 hitherto employed have been greatly inferior, in their optical 

 powers, to the reflecting telescopes of Herschell. A tele- 

 scope, therefore which would bear a comparison with them, 

 in those relations, and which had a decided superiority in 

 its micrometrical apparatus, was very fit for obtaining inter- 

 esting confirmation and giving greater extension to prece- 

 ding discoveries. That which appears to me the most im- 

 portant (says Prof. Struve) was to undertake with the tele- 

 scope of Fraunhofer, a review of all the stars of a certain 

 brightness, in that portion of the sky, visible to me, in order 

 to ascertain which among them is double. I entertained 

 the hope of obtaining more positive knowledge on the man- 

 ner of distinguishing stars physically and optically double, 

 in order to be able to deduce some general views of the 

 manner in which these stars are distributed over the celes- 

 tial vault. 



It is only under the equator that the whole sky can be 

 perceived, by the earth's rotation, while at each pole, but 

 one half is visible. In the latitude of Dorpat 12H° of the 

 sky can be seen, viz. from the pole to 31 1° south of the equa- 

 tor. But the southern stars rise too little above the horizon, 

 to be successfully examined even by the most powerful in- 

 struments, for at those small altitudes the inferior strata of 

 the atmosphere, produce a trembling in the image. I re- 

 solved in consequence to extend my review only to 1 05° from 

 the pole, or 15° south of the equator. In this space the 

 lowest stars were still 16^° above the horizon at their meri- 

 dian passage. I divided this interval into twelve zones, 

 according to the distances from the celestial poles and made 



