CHAPTER III 



ADJUSTABLE AND IMMERSION OBJECTIVES; REFRACTION AND 

 COLOR IMAGES; BINOCULAR MICROSCOPES; CARE OF THE 

 MICROSCOPE; CARE OF THE EYES; WORK TABLES; TEST- 

 ING THE MICROSCOPE; MARKERS AND MECHANICAL 

 STAGES; ROYAL MICROSCOPICAL SOCIETY STANDARDS 



133. Apparatus and material for Chapter III. 



1. Compound microscope with dry, 7. Histological specimens like mus- 

 Wfcter, and homogeneous immersion cle fibers, etc. 



objectives. 8. Cedar oil, xylene, chloroform, 



2. Simple microscope. glycerin, and lens paper. 



3. Eye shade (fig. 56). 9. Binocular microscope. 



4. Shield for microscope and ob- 10. Opaque objects like insects, 

 server (fig. 33). feathers, etc. 



5. Slides and cover-glasses (Ch. n. Mounted fly's wing. 



X). 12. Markers, mechanical stages, 



6. Pleurosigma ( 115) and stained colored shellac and camel's hair 

 bacteria. brush for pointers. 



ADJUSTABLE, WATER AND HOMOGENEOUS IMMERSION OBJECTIVES 



Experiments 



134. Adjustment for objectives. As stated above (31) the 

 aberration produced by the cover-glass (fig. 51) is compensated for 

 by giving the combinations in the objective a different relative posi- 

 tion than they would have if the objective were to be used on uncov- 

 ered objects. Although this relative position cannot be changed in 

 unadjustable objectives, one can secure the best results of which the 

 objective is capable by selecting covers of the thickness for which the 

 objective was corrected. (See table, Ch. IX.) Adjustment may be 

 made also by increasing the tube -length for covers thinner than the 

 standard and by shortening the tube-length for covers thicker than the 

 standard. 



In learning to adjust objectives, it is best for the student to choose 



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