284 Permanence of the Rutherfurd Photographic Plates. 

 page 104, line 13 from bottom, 

 for: 



wt =1/3 sin 2(pBee'' (<p — d) seed cos {I -\- (>) cosecZsin^ i sin i", 

 put : 



it'a =/3cos'^0sec '^((p — d) sin- i™ sin i^^, 

 for : 



[1.130S — 10] 

 put : 



[1.7328— 10]. 



These changes in the refraction formulae cause the discordances 

 between the results of M. Henry's reduction and my own to dis- 

 appear almost completely. 



Another small quantity which I neglected, and which appears 

 to have been neglected also by M. Henry, arises from the quantity 

 c, or the error of centreing the plate in declination. It is easy to 

 see that the values of Aa obtained in my paper require the cor- 

 rection : 



d An = -\- c Ai (x see ')). 



