ULTRAMICROSCOPES 73 



In this new Immersion Ultramicroscope 1 both the illuminating 

 and observing objectives are beveled at the ends so as to allow 

 their front lenses to be brought very close together with their 

 axes at right angles; the drop of liquid to be examined is 

 placed between the front lenses, clinging by capillarity. No 

 cell is employed. The light rays having but a very short dis- 

 tance to travel, even dark colored liquids may be studied. Diffi- 

 cultly cleanable, expensive cells are thus wholly eliminated, the 

 amount of material required for study reduced to a minimum, 

 and the images obtained are exceptionally brilliant. 



For the study of hydrosols, water immersion objectives must 

 be used, but for colored glass and similar bodies homogeneous 

 immersion objectives are required. 



The construction of the instrument is shown in the diagram, 

 Fig. 33A. Fitted to the body tube of a compound microscope 

 is the objective carrier C into which slides a plate to which is 

 screwed the image-forming objective O. To the stage of the 

 instrument is attached the mechanism supporting the illuminat- 

 ing objective I. The micrometer screws S 1 , S 2 , S 3 provide means 

 for the exact adjustment of the beam of light passing in the 

 line of the axis of the objective I, so that it will fall normal to the 

 optic axis of the microscope. S 1 gives an up and down adjust- 

 ment, S 2 forward and back and S 3 from side to side. By rack 

 and pinion S 4 , the entire illuminating device can be lowered for 

 cleaning, for the removal of the objectives, etc. When raised 

 in position for use, the screw s is turned, thus locking the mecha- 

 nism in place. 



The trough T serves to catch any drip when the liquid is being 

 applied between the objectives. 



When in use, the instrument is placed on a bed plate with 

 saddle stand upon an optical bench of the type shown in Figs. 

 24 and 30. An apparatus consisting of a condensing lens and 

 an adjustable slit, also on saddle stands, serves to throw a 

 beam of light from a radiant (arc or Nernst lamp) into the 

 objective I. 



In critical work the ocular of the microscope is furnished with 

 1 Made by C. Winkel, Gottingen, Germany. 



