CH. IX] 



HIGH POWER MICRO-PROJECTION 



281 



406. Range of objectives to use with a substage condenser. 



Objectives of 16, 12, 10, 8, 6, 4, 3, and 2 mm. equivalent focus 

 are used with the substage condenser. For objectives of longer 

 focus than 16 the substage condenser of the ordinary form is 

 rarely used. Either a special long focus substage condenser is used 

 or the ordinary one is turned aside and the cone of light from the 

 large condenser used as directed above ( 376). 



407. Change in position of the substage condenser for differ- 

 ent objectives and thickness of slides. For the highest powers 



FIG. 156. PROJECTION MICROSCOPE OF ZEISS. 



(From the 4th edition (1899) of Zeiss' catalogue of instruments and appliances 

 for Photo- Micrography and Projection). 



This projection apparatus, which in its main features was described in Zeiss 

 microscope catalogue No. 28, (1889), and No. 29 (1891), consists of an 

 optical bench on which all of the parts needed move separately so that any 

 desired arrangement can be made for projection of large objects with low power 

 or smaller objects with high powers. 



Commencing at the right: 



/ Arc lamp with inclined carbons, and with fine adjustments to center the 

 source of light (crater of the positive carbon). 



2 First element of the condenser consisting of a meniscus and a plano- 

 convex lens, to render the light beam parallel. 



3 Water-cell. 



4 Second clement of the condenser to converge the light-beam. 



5 Iris diaphragm to cut down the light-cone if desirable. 



6 Stage and substage condenser. 



7 Projection objective and fine focusing device. In the figure no ocular 

 is used. 



This arrangement of the parts enables the user to employ a microscope with 

 oculars or amplifiers, or the simple apparatus here shown, or photographic 

 objectives. 



