Mr. jeau rat's Account of 
136 
Abe Application of the general Formula to the particular 
-cafe of the equal lenfes a and c. 
Let 
The relation 
/ = 0,2361 F, 
found for the 
focal diftances, 
gives 
ad~f, the focal diflance of the lens A, 
r F, the focal dill, of the lenfes a and c, 
tfArrF— f~ 0,7639 f, the dift. between thefe lenfes, 
abzzf — 2/== 0,5278 F, diflance, 
< bd “ 2 x f —/= 1,5278 f, diflance, 
2 fX¥-f n 
bcz- — - —0,291 8 f, diitance, 
F+/ 
2 F X F f 
cd~ ~ 1,2360 f, diflance, 
L F+/ 50 ? 
Abe 
application de la for mule generale au cas partictilier des lent Hies egales a and c, 
Soit 
Le rapport trouve des 
foyers /= 0,2361 F,<{ 
donne 
ADrl 1 , foyer de la lentille a, 
aBzz/zzOyZ ^ 1 F » foyer des lentilles a and c. 
^a = f— /= 0,7 639 F, diflance entre ces lentilles, 
ab = f — 2/0=0,5278 F, diflance, 
bd = 2 (f—/) = 1,5728 F, diflance, 
ec=i— — fl — 0,2918 f, diflance, 
F +/ 
2 F( F — /) 
F+/ 
= 1,2360?, diflance, 
application 
