DR. R. A. SAMPSON ON A 



alao the second lens of the corrector 0....(V. with curvatures, M given on p. 49, but 

 increasing the thickness to '015000, is 



r i, 1 ft, +-oi5oool J i, 



[-'001267, + -657895J [* 1 J [-r357552, + T520000. 



+ '999981 + '009868 | 

 -T359452 +'986604j 



!IM<1 !, * 1 Jl, + '0150001 f 1, * 1 



-'001292, +'651381 J I* 1 J L-1'397234, l'535200j 



+ '999981, + -009771] 



|> [n+Sn], 

 -1-399190, + '986348 J 



Hence the whole combination gives 



330582, +1-3619341 r + 1'010127, + '9292101 f+ '999981, +'0098681 

 -'208333, +2-166667 J 1+1-428571, +2'304108 J [-1-359452, + '986604 J 



+ '140265, +3'457413l 



-'198450, +2'237713 J 

 and 



'330672, +1-3615081 f + 1'010393, + '9293701 f+ '999981, +'009771 1 

 -'208522, +2165574 J[ + 1-470892, +2'342197 J [ + 1'399190, +'98634sj 



+ '140291, +3'45733G] 



[n+Sn]. 

 -'198480, +2'236730J 



Hence for n + Sn there is an excess in the coefficient G of 26 units ; to correct this, 

 guided by previous experiments, I made a trial change in (K 2 ), which refers to the 

 lens of the reverser, of 1220 units, so that 



(K a ) = -'010297-'001220 = -'011517. 

 This gives, to redetermine the reverser, supposing its power is to remain unchanged, 



- l W,(l + tJc a )* = + '875000, 

 fcs = (n-l)B 2 , *,= +'020000, 



B,= +'472584, B',= +'451898, 



