GHEAT REFRACTING TELESCOPE AT ELCHIES, IN MORAYSHIRE. 



383 



rally the case with a given 2 result, such a reference must be looked on with 

 exceeding respect. But Struve observing with the later 9-inch Dorpat, is a 

 very different person in his results from the same Struve working with the 

 earlier 3()-inch Dorpat, or the result given as " o-;" and it is chiefly on the (7-2, 

 than the 2 - 2', that the argument for change in the star 35 Piscium used to be 

 founded. The argument, though weak, was no doubt contributed to also by the 

 H^ and S observation, and in a more exceeding degree ; but if I am right in my 

 belief that the small size of Struve's earlier telescope is the reason of the <t results 

 being always greatly inferior in accuracy to those marked 2, — then a similar cause 

 should act and to a large extent in vitiating the excellence of an " H^ and S " 

 result, transcending though the natural observing powers of these eminent men 

 may have been. In fact, too, we shall soon find, before we have gone very far 

 through our list, that the limits of error of "H^ and S" are decidedly large; 

 and though those of the excellent " H^ " are often larger (by reason of the imper- 

 fect mounting, rather than the defective size, of the instruments he employed), 

 yet in this case it would have been better to take a mean between them all, than 

 to have altogether rejected H\ If too such a mean be now taken, then all the 

 rest of the results, including that of Elchies, confirm my father's view of the cos- 

 mical constancy of this star-group in distance as well as position. 



But in character^ what are they, these two stars ; do they form a physical or 

 an optical pair ? Now extreme relative fixity, such as here prevails, has usually 

 I believe been put down as implying that a pair is optical only ; and our proper 

 motion table, on page 380, will enable us at once to test that hypothesis on the 

 foundation there adopted ; for the large star has so sensible an amount of proper 

 motion attributed to it, that in thirty years the angle of position should have 

 increased by no less than 12 degrees, and the distance lessened by 2-3 seconds, 

 if the larger is not carrying the smaller orb along with it in its flight. But as we 

 have already seen, no such change has occurred, certainly nothing equal to the 

 twentieth part of what is here indicated; we are therefore justified (subject always 

 to the correction of the British Association Catalogue), in considering the pair to 

 be a physical double star, or a binary with extremely slow orbital movement. 



(2.) 65 PISCIUM, Approx. R.A. Q'^ 42n» 28= ; Decl. -{■ 26° 57' 31", January 1, 1862. 



Com- 

 ponents. 



Magni- 

 tude. 



Colour. 



Position. 



Distance. 



Date. 



Authority. 



A 

 B 







AB 300 57 



4''o 



1783-15 



Ha 



A 















B 







AB 297 22 





1802-61 



H,. 



A 















B 







AB 295 48 





1822-86 



H2 and S 



VOL. XXIII. PART II. 



5 M 



