MICROSCOPE LAMPS 



165 



a which is attached to the end of the body tube of the micro- 

 scope. The screws S, S', turned by a small key, permit the 



FIG. ioo. Bausch & Lomb Clutch 

 Objective Changer. 



FIG. 101. Leitz Clutch Objective 

 Changer. 



accurate centering of each objective. This is the best type of 



device when centering is essential, but requires a special box for 



holding the objectives to which the blocks b have 



been attached. With the clutch or clamp type 



(Figs, ioo and 101) the ring is of such diameter 



as to permit placing the objectives in their 



usual brass boxes. 



Sedimentation Glasses. The apparatus illus- 

 trated in Fig. 103, commonly known as Spaeth's 

 sedimentation glass, will 

 be found a most useful 

 laboratory device. The 

 liquid containing the 

 sediment to be examined 

 is poured into the glass 

 with its stopcock up as 

 shown. After subsidence 

 has taken place gentle 

 stirring will dislodge any 

 material clinging to the 



sides of the vessel and this will fall to the bottom. The stop- 

 cock is now turned a quarter turn and the liquid emptied out. 

 The stopcock can now be removed with the sediment contained 

 in the conical depression and with but very little of the super- 



FIG. 1 02. Zeiss Centering 

 Objective Changer. 



FIG. 103. Spaeth Sed- 

 imentation Glass. 



