MICROSCOPES. 



31 



Fig. 15. Fig. 16. 



19. METHOD OF MEASURING THE MAGNIFYING POWER OF 

 MICROSCOPES. We purpose in the next place to explain the method 

 of ascertaining the magnifying power of the compound microscope ; 

 and we are the more anxious to do this, for the reason that it is a fault 

 too common amongst the makers of these instruments to exaggerate the 

 power of the apparatus. The mode of measuring the magnifying 

 power of the compound microscope is generally taken at the assump- 

 tion, that the naked eye sees most distinctly at the distance of ten 

 inches. Place on the stage of the instrument, a known divided scale ; 

 and when it is distinctly seen, hold a rule ten inches from the dis- 



