MICROSCOPICAL GLOSSARY 



Abbe (pronounced ab'-eh), Ernst (ob. 1905), i)rf)fe.ssor in Jena, 

 founder of Carl Zeiss Stiftuns, developer of theory of the microscope, 

 and inventor of many microscopical improvements. 



Abbe camera. Camera lucida, with a perforated diagonal silver 

 layer in a glass cube (Abbe cube) (Zeiss). 



Abbe condenser. Usually the immersion 2- or 3-lens uncorrected 

 condenser, of 1.2 or 1.4 nominal aperture, commonly used dry. (Also 

 rarely an achromatic condenser with long focus, large image, and aperture 

 near 1.0.) (Abbe.) 



Abbe illuminating apparatus. Rackwork substage, with a second 

 rackwork for lateral movement of the iris of the condenser, and also 

 provision for rotation of this. Useful only for testing objectives, and 

 for oblique pencils of light. (Abbe.) 



Abbe test-plate. Ruled lines in a layer of silver deposited under a 

 cover-glass of varying thickness. Useful for testing objectives, espe- 

 cially for star test. (Spitta, Siedentopf, Zeiss.) 



Aberrations. Differences between the actual and the required course 

 of light in uncorrected or insufficiently corrected lenses. Chromatic 

 aberrations are due to the differing wave lengths of which white light 

 is a mixture. Spherical aberrations are mainly due to the spherical 

 form of lens surfaces, which is usually compulsory. (Abbe, Czapski.) 



Absorption. Removal of light (usually by its change into heat). 

 Often only for a short range of color (absorption band in spectrum). 



Absorption of color. The color of a transparent substance (such as a 

 stained section mounted in balsam) is of course due to its absorption 

 of the complementary colors. Thus a yellow-green screen (such as 

 Wratten No. 58) absorbs most of the red, blue, and violet. 



Accommodation. Focusing of the eye, by changes in shape of the 

 crystalline lens, to suit distances, varying from indefinitely far to 8 

 inches or less. Accommodation may vary with age from 14 diopters or 

 so to zero. 



Achromatic. Lens or combination corrected more or less perfectly 

 for (axial) color aberrations; which includes some correction for spherical 

 aberrations also. The back doublets or triplets of a high-power objec- 

 tive are not strictly to be called achromatic, since they ha\e the large 

 excess of corrections required to compensate for the uncorrected front 

 lenses. 



Achromatic condensers. Corrected by combinations of flint and 

 crown lenses; either mainly in the axis; or, by following the sine law, 



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