146 PROCEEDINGS OF THE AMERICAN ACADEMY 



To which must be added, that the first hypothesis requires an in- 

 crease of distance between 1862.2 and 1863.2 of 0".8 ; the third, a very 

 slight diminution ; but observation indicates a diminution of about 

 0".55, a quantity, to use Mr. Rutherfurd's expression,* " so small that 

 its existence cannot be asserted with confidence." It is hardly conceiv- 

 able that the long and careful series of observations of Mr. Rutherfurd 

 should be in error 3°.3 ; and also inconceivable that Professor Bond's 

 measures, agreeing as they do within 2° 20' among themselves, should 

 be in the mean 5°. 4 erroneous. 



We have, therefore, nothing to oppose to the hypothesis that the new 

 companion is the disturbing body, but the very improbable supposition 

 that the small star partakes very nearly in the great proper motion of 

 Sirius without physical connection ; or the second hypothesis, that the 

 new star is in the system, but with small mass. If this is the case, the 

 disturbing body must, in lieu of the small light of the companion, have 

 still less, or even be absolutely invisible. It is consequently highly 

 probable that the disturbing body has been actually found ; that what 

 was predicted by theory has been confirmed by sight. The importance 

 of continued observations on Sirius cannot be too highly felt. The 

 companion must be measured the coming year, and for several years ; 

 while Sirius itself should be i-e-observed with meridian instruments. 

 So far as the right-ascension element is concerned, a series of observa- 

 tions is now in progress at Cambridge ; while Captain Gilliss has most 

 obligingly consented to make a series of declination-observations at 

 "Washington ; and the standard observatories at Greenwich and Paris 

 will doubtless continue their series of fundamental star observations, 

 including, of course, Sirius. 



I am much obliged to Mr. Rutherfurd for the communication of the 

 details of his observations in 1863, and hope he will publish them, 

 together with similar details of those of 1862, and others to be made 

 hereafter. The subject is one where the co-operation of several 

 observers is desirable. Full certainty here can only be obtained after 

 several years' observations. 



On motion of the Corresponding Secretary, the meeting was 

 adjourned to Tuesday, the 9th of June. 



* As before, American Journal of Science for May, 1863, p. 407. 



