COMPOUND MICROSCOPES 17 



microscope is lighted again. Immediately above the analyzer 

 and attached to the mounting of the analyzer a lens of a com- 

 paratively long focal length has been placed in order to over- 

 come the difference in focus created by the introduction of the 

 analyzer into the optical rays. 



The condensing system is mounted on a slider, and, further- 

 more, can be raised and lowered along the optical centre by 

 means of a rack-and-pinion adjustment. If lowered sufficiently, 

 the condensing system can be thrown to the side to be removed 

 from the optical rays. The condenser consists of three lenses. 

 The two upper lenses are separately mounted to an arm, which 

 permits them to be tilted to one side in order to be removed 

 from the optical rays. The complete condenser is used only 

 in connection with high-power objectives. As far as low-power 

 objectives are concerned, the lower condensing lens alone is 

 made use of, and the latter is found mounted to the polarizer 

 sleeve. Below the polarizer and above the lower condensing 

 lens an iris diaphragm is found. 



The microscope table is graduated on its periphery, and, 

 furthermore, carries a vernier for more exact reading. 



The polarization microscope is not furnished with an ob- 

 jective nose-piece. Every objective, however, is supplied with 

 an individual centring head, which permits the objective to be 

 attached to an objective clutch-changer, situated at the lower end 

 of the microscope-tube. The centring head permits the objectives 

 to be perfectly centred and to remain centred even if another 

 objective is introduced into the objective clutch-changer. 



At an angle of 45 degrees to the polarization plane of polarizer 

 and analyzer, a slot has been provided, which serves for the 

 introduction of compensators. 



Between analyzer and ocular, another slot is found which 

 permits the Amici-Bertrand lens to be introduced into the 

 optical axis. The slider for the Bertrand lens is supplied with 

 two centring screws whereby this lens can be perfectly and 

 easily centred. The Bertrand lens serves the purpose of 

 observing the back focal plane of the microscope objective. In 

 order to allow the Bertrand lens to be focused, the tube can be 

 raised and lowered for this purpose. An iris diaphragm is 

 mounted above the Bertrand lens. 



