Permanence of the Rutherfurd Photographic Plates. 283 



NOTES. 



Note on Prof. Jacoby's Paper on the Reduction of Stellar 

 Photographs. (Annals Yol. IX. p. loi.) 



M. Prosper Henry has kindly pointed out (^Bull. du Com. 

 Perm. Tome 3) that the above paper contains an inconsistency, 

 inasmuch as I have used the true declination of the centre of the 

 plate instead of the apparent declination in computing the trans- 

 formation tables. The very slight effect of this might be neg- 

 lected, were it not for the fact that it can be taken into account 

 fully by slightly changing my refraction formula for .x. The 

 changes required are : 



page 104, line 8, 

 for : 



put : 



J/^ = /3(i-f S"2)sini^^ 



page 104, line 15 from bottom, 

 dele : 



tau Z = 2 tan <j> 



page 104, line 14 from bottom, 

 for : 



ivi = /3 cos f sec (0 — cJ) sec d sin i'^ 

 put: 



tt'i = it sin i" , 



