68 
No. 
34 
Revolving Nose-pieces. 
a) Revolving nose-piece for 2 objectives. 
(Fig. 26.) 
MarJcs 
20. 
Fig. 26. 
Fig. 27. 
Revolving Nose-pieces. 
b) Revolving nose-piece for 3 objectives. (Fig. 27.) 
c) Revolving nose-piece for 4 objectives .... 
27. 
35. 
25 ^Sliding Objective-changer. TMs apparatus is so ar- 
ranged that each individual objective can be centered and it 
permits the use of any number of glasses. (Fig. 28 and 29.) 
It consists of: 
a) The tabe-slide. This is screwed on tlie end of the body 
like an ordinary nose-piece with t h e s 1 i d e o p e n i n g towards 
the front. The plane of the sliding motion is not made at 
right angles to the optic axis but inclined at a small angle to it. 
b) The objective-slide. The plane of the slide is inclined 
to the axis at an angle corresponding to that of the tube-slide, 
so that the objective rises on being withdrawn and cannot damage 
the specimen. At one end of this fitting is a screw turned by a 
watch-key which acts as a stop in bringing the objective always 
back to the same position and also serves as a centering ad- 
justment in the direction of the slide, while the adjustment in the 
transverse direction is effected by a similar screw working at 
right angles to the first. 
