ASTRONOMY AND METEOROLOGY. 375 



him for the Nautical Almanac of the Greenwich observations of Mars, 

 he " was struck with the fact that the clock-errors given hy a Virginia 

 differed everywhere from those given hy other fundamental stars, in 

 such a manner that the right-ascension of that star given by the Tabu- 

 la. Rcgiomontance appeared to be too great." Consultation with Lieut. 

 Davis and Prof. Peirce prompted him to pursue the matter further, 

 and after he had, on account of some deviations in Canis Majoris, 

 concluded to omit that star from the number of comparison-stars, he 

 was, upon mentioning to Prof. Peirce his supposition of a change in 

 the proper motion of a Virginia, reminded that Bessel had made a 

 precisely similar supposition in the case of the former star. After 

 going into an elaborate investigation, Mr. Schubert says: "In this 

 table, then, the decrease of the differences until about the year 1783 

 is distinctly appreciable, as well as their increase afterwards in nearly 

 the same ratio. This diminution of the differences up to the year 

 1783, and the subsequent decrease, correspond to an increase of the 

 relative right-ascension, and to a subsequent decrease of it. I think 

 it thus placed beyond all doubt that there are variations in the proper 

 motion of a Virginia." Bessel has noticed a similar increase of the 

 relative right-ascension of Sirius till 1794, where the difference is at 

 its maximum, though he somewhat distrusts his result. This new 

 case, however, confirms in a most striking manner the truth of that 

 result. After some further investigations, Mr. Schubert concludes 

 that the period for a Virginis is about 44 years, while Bessel's suppo- 

 sition of a period of 50 years for Sirius is confirmed. 



" Bessel suspected that the stars which exhibit such irregularities 

 move round dark bodies. Since the conviction has been forced upon 

 me that such changes are common to all the fixed stars, although in 

 most cases insignificant or included in long periods, I must venture to 

 differ from Eessel's opinion, at least in some measure. There may 

 exist peculiarities in the motion of the fixed stars in space which pro- 

 duce such variations in the proper motion, but which, together with 

 their causes, we are not yet able to explain. A fixed star round which 

 large and very distant planets are moving, admitting almost of being 

 considered as revolving fixed stars, but invisible to us, will not itself 

 move in the curve of the proper motion, but this curve will rather be 

 described by the common centre of gravity." 



In the Astronomical Journal, No. 18, Prof. Peirce examines this 

 paper and its subject, and concludes as follows: "On the whole, 

 then, the weight of the argument appears to be in favor of the suppo- 

 sition that Spica is moving around some centre, which is not far' distant 

 from it." 



THE PARALLAX OF GROOMBEIDGE 1,830. 



STRUVE, in a paper presented to the French Academy on Jan. 28, 

 gives the following as the result obtained from a long series of obser- 

 vations conducted with the most extraordinary care upon the paral- 

 lax of the star Groombridge 1,830. " The parallax found equal to 

 -f-0".034 surpasses so little the probable error of 0". 029, that it would 



