MICROSCOPIC OBJECTS. 121 



corded silks and moreens by the pressure of two pieces 

 passed between rollers." There can be no doubt now, 

 that the spine-like markings on the scales of the Podura 

 are in fact impressed portions of the lines. The very 

 perfection of a microscope in giving distinct vision only 

 in one plane at a time is Hable to occasion an erroneous 

 idea of an object, if not taken into account ; and this is 

 one example. 



