50 THE POPULAR SCIENCE MONTHLY. 



Pardon these figures ! But they form the basis of the reasonings 

 which constitute the groundwork of this article, and it is essential to 

 consider them in order to know on what to rely in discussing the sys- 

 tem of Sirius. In comparing these last numbers with those of the 

 preceding ephemeris, we see at the first glance that the angle dimin- 

 ishes more rapidly than had been announced, while the distance has 

 continued to increase since 1870 instead of having attained its maxi- 

 mum on that year, as the orbit of Auwers indicated. It is still fur- 

 ther shown by the diagram I have constructed that the arc of the 

 observed orbit crosses the calculated orbit about 1668 and is pro- 

 jected outside of it, pursuing a wholly different curve which must be 

 larger than the orbit traced and less eccentric. 



If the observed motion were the mean motion, the revolution of 

 the satellite would be accomplished in a period of about one hundred 

 and sixty-seven years. But the arc passed is yet too small to allow 

 any positive conclusion, and, as the observed perturbations of Sirius 

 demand a period of forty-nine years, Ave are brought to the conclu- 

 sion that the observed companion continues to accelerate its motion 

 and will be found in the west of Sirius in 1892, or else there is another 

 body causing perturbation nearer Sirius, and moving more rapidly. 



We should reserve all conclusions in regard to the existence of 

 these other satellites, as well as all difference of period between the 

 observed orbit and the calculated orbit; but the inevitable conclusion 

 is, that the observed positions do not correspond with those of the 

 ephemeris, and that the orbit thence resulting differs from the calcu- 

 lated orbit. 



By the aid of all the observations I have constructed the figure, 

 which shows the movement of the observed planet from 1862 to 1877. 

 The central disk represents Sirius ; the four cardinal points are indi- 

 cated by dotted lines ; the proper movement of Sirius in space is 

 marked by the large arrow, whose length corresponds exactly to this 

 movement during ten years (the figure is drawn to the precise scale 

 often millimetres for a second). If the small star discovered in 1862 

 to the east of Sirius did not belong to it, if it was situated in the 

 depths of space far beyond, it would have remained fixed, and Sirius 

 would have moved from it in the direction indicated by the arrow. 

 But, on the contrary, it belongs to Sirius, accompanies that sun in its 

 progress as the earth accompanies its sun, and turns around it in an 

 elliptic orbit. It has yet traversed, from 1862 to 1877, only the line 

 marked on the future a curve not lomr enouech to enable us to calcu- 

 late the remainder of its orbit. As it is seen, this star is quite small 

 by the side of Sirius, but still larger than Jupiter relatively to our sun. 

 Is it an immense planet, totally opaque and shining only by reflection 

 of the light of Sirius? This is not probable; it must still be self- 

 luminous just as our own earth was during so many ages. It does 

 not correspond exactly to the observed perturbations, a fact which 



