with complete Color Correction. 433 
Oase I. a B t 
siete 8 v 7 0 
LEE. v T * 
mare 2S & w 0 
giving values for the curvature sums: 
: B. 0. 
Yr 3°47026 1-20807 — 835472 
IL. 9°47513 1428004 21°23685 
ITI. 158585 1157425 —16°59076 
IV. 11°67459 18°10299 —27°22301. 
Substituting these values in the general formula (1) we derive 
or F the following, the first column giving the Fraunhofer 
ray for which the focal length is computed : 
TasBLE III. 
X: IL. Til. 
A —- 1°00002 Hae Ss Ee 100000 
B 1°00000 99949 -99989 “99 
U 99999 1:00043 1:00102 1:00053 
D 99999 1:00026 1-00052 1°00005 
E 1:00024 99992 99942 99993 
F 99999 99988 “99951 99999 
G -99999 1°00002 1:00030 100000 
To exhibit more distinctly the improvement in this form 
over the double objective, I arrange the differences in the above 
values between each and the true focal length of that system 
in a table, supplementing it with a sixth column in which are 
entered the corresponding differences for a double objective of 
song a and f with its best color correction, and having a 
ocal length of unity. 
TABLE IV. 
L rea lil. IV. ¥; 
A ie fe ae 3 +135 
B +1 —53 9% —35 + 66 
Cc 0 +41 +91 +50 + 41 
D 0 +28 +41 ~ 0 
E +25 pe ~— 67 —10 + 13 
F 0 — —60 Ets 
G 0 +2 +21 = 3 +287 
The large difference in F, is owing to an erroneous value 
of ng in Fraunhofer’s Flint 13. 
be they are multiplied by large 
That these differences A not 
