A. MATHEMATICS AND ASTKONOMY. 25 



authority in science, of a new edition of the ten-figure loga- 

 rithmic tables of Vlacq. He maintains that the business in- 

 terests of trade have to some extent caused this interval of 







two hundred and fifty years to elapse between the original 

 imperfect and the present perfect set of tables, and that per- 

 fection in these matters can only be attained by the action 

 of a permanent scientific or national authority, which shall 

 conscientiously publish, from time to time, such errors as may 

 be discovered in the new tables. 3Ionthly Notices Roy.Ast. 

 /S'oc.,1873. 



IMPOKTANT ASTKONOMICAL DISCOVERY. 



A discovery, which, if confirmed, is one of the most im- 

 portant of the year, is announced from the Poulkova Observa- 

 tory. It is that of a minute companion to the bright star 

 Procyon. It derives its importance from being supposed to 

 be the body whose attraction has caused certain irregularities 

 in the motion of Procyon which have been known to exist 

 for several years. This discovery is so near a counterpart to 

 a similar one made in the case of Sirius, that it may not be 

 uninteresting to narrate some circumstances connected with 

 and growing out of the latter. 



It has been known for about forty years that the well- 

 known star Sirius, the brightest in the heavens, was subject 

 to an oscillating motion which could be accounted for by 

 supposing a satellite moving around it. The orbit of the 

 satellite was calculated by Peters and Auwers, though no 

 one had ever seen it. But when Alvan Clark & Sons, of 

 Cambridge, completed their great object-glass of eighteen 

 inches' diameter in 1862, they turned it on Sirius, and saw a 

 satellite, which, as it afterward proved, was in the direction 

 of that suspected. Its motion has since corresponded so 

 nearly with that of the calculated body as to leave no serious 

 doubt of their identity. For this discovery, as well as for 

 making the telescope, Alvan Clark received the La Lande 

 medal from the French Academy of Sciences in the year 

 followino;. 



It was afterward found, by the very profound and minute 

 investigations of Dr. Auwers, that the movements of Procyon 

 could be accounted for by the attraction of a satellite re- 

 volving round it in forty years. There could be no doubt 



B 



