58 
Fig. 18. 
Abbe Illuminating apparatus. 
) Condenser system of 1.20 num. apert., b) condenser system of 1.40 num. apert., c) cylinder 
diaphragm, d) iris diaphragm, e) milled head for throwing the diaphragms out of centre. 
The Condenser system — made as before in two foi'iiis. 
a) a double combination of 1.20 num. ai)ert., and 
b) a triple combination of 1.40 num. apert., 
is mounted in a holder which fits a sprung jacket on the ajjparatus. 
This arrangement facilitates an interchange of the two condenser 
systems, and also serves to carry the following apparatus when 
the condenser is not used : 
c) the ordinary cylinder diaphragm; 
Marks 
