PHILADELPHIA 
The SLibstage is composed of three parts, arranged one above the other. 
The upper part consists of a fixed ring, supporting the removable Iris 
diaphragm. This diaphragm is operated by a lever, easily accessible from the 
front of the substage, and is so arranged as to come directly in contact with the 
object slide or lower, as desired, thus it can be placed in the most effective 
position for use without the condenser. The middle section of the substage is 
movable vertically on the main substage axis and consists of a ring, with centering 
screws, carrying Abbe condenser, 1.20 N. A. The condenser ring swings laterally 
to the left of the instrument in such a manner that the condenser is entirely out of 
the path of rays from the mirror, and is also perfectly free for changing accessories. 
The condenser ring, the arm on which it is carried, and the sliding support are all 
of the most stable construction, so that there is perfect rigidity and accuracy of 
centering throughout. The vertical adjustment of this section of the substage per- 
mits the condenser to be brought in immersion contact with the object slide or to 
be placed in any other position desired without reference to the position of the 
upper Iris Diaphrag;m. The lower section of the substage carries the large Iris 
Diaphragm which is used below the condenser. This diaphragm may be swung 
from under the condenser to the right of the instrument. It is so mounted that it 
may be rotated upon its own axis and is laterally movable by rack and pinion 
when oblique illumination is desired. 
