CHAPTER VI 

 THE ROUTINE MICROSCOPE 



Routine Microscopy. — In most of this book, the micro- 

 scope is treated from the optical standpoint, and the utmost 

 it can perform is demanded from the instrument. But for 

 routine work, and also for many kinds of investigation, the 

 possible performance of the instrument may be much 

 beyond the demands which are made on it. In this case, 

 it would often be a waste of time to attend to every nicety 

 of manipulation, for the commonest optical errors (such 

 as too low condenser aperture, slightly wrong cover-glass 

 thickness, sUghtly wrong centering, and slightly wrong 

 tube length) can usually be hidden by using a lower magni- 

 fication with the same objective. Thus, a lower eyepiece 

 is employed than would be used if the maximum useful 

 magnification were to be aimed at. This maximum useful 

 magnification could not, of course, be attained in this case; 

 for the images would become dull and soft, from the optical 

 defects, if high eyepieces were employed. Such a use of 

 low eyepieces is, therefore, forced on the routine worker 

 if he wants a sharp and bright image, along with uncor- 

 rected optical errors. It becomes merely a question of 

 what grade of useful magnification suffices for the worker; 

 or what degree of dullness, softness, or glare he may have 

 to put up with without spoihng the image for his particular 

 purpose. 



With an eyepiece magnifying 5 times (modern notation) 

 it is evident that the common l.S-milhmeter oil-immersion 

 objective of 1.3 aperture (magnifying 100 times) gives an 

 image magnified 500 times on the standard microscope. 

 This image is usually fairly clear, if the lenses are clean, 

 and there is no gross error. Many routine microscopists 



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