63 



From these are deduced the sides of the triangle formed by 49, 

 a, and 55 Cygni. 



The sides of the triangle formed by a, 55 and 57. 



Hence it is evident that 49, a, 55 and 57 Cygni have preserved, 

 within the errors of observation, the same relative positions for the 

 last 70 years. 



VOL. XV. 



