quality, or resolution, of the image rather than 

 mere magnification, per se, that concerns the mi- 

 croscopist, it becomes obvious that the objective is 

 the most vital part of the instrument. For on its 

 performance in giving sharp distinction to ex- 

 tremely minute structural details, depends the 

 eyepiece; the latter lens system acts only further 

 to magnify, and not resolve, the image already 

 formed. In other words, if either a sequence of fine 

 lines or an assemblage of dots whose diameters, 

 and whose distances apart, are no greater than, 

 say, 3/250,000 of an inch, are viewed with an ob- 

 jective of high magnifying power but poor resolv- 

 ing properties, the resulting image will be but a 

 blur; conversely, a good lens comparatively lower 

 in power, will separate these dots and lines caus- 

 ing them to stand out distinct and clear. There- 

 fore, the limits to which magnification may be 

 carried are infinite; but beyond certain points their 

 attainment would be worthless, for, unfortunately, 

 the resolving power of lenses is fixed by certain 

 physical factors which have to do with the nature 

 of the glass with which they are constructed and 

 the amount of light they can transmit. 



Even the ultra-microscope, which has recently 



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