PROPERTIES OP LENSES. 21 



Second, because under different conditions of aper- 

 ture different objects assumed the same form. 



Now Professor Abbe himself says ' ' minute struc- 

 tural details are not as a rule imaged by the Micros- 

 cojie Diojytrically , in accordance with the real nature 

 of the object." 



Some, less enamoured of the metaphysical aspect 

 of the question, may find it difficult to perceive that 

 images formed optically and dioptrically give us just 

 as little information as to the real nature of the 

 object. 



If two scarlet cloths the same size, one marked 

 with black squares the other with circles, and one 

 coarser than the other, be placed at such a distance 

 that their images subtend small angles, they will 

 appear identical. If brought nearer, or what is the 

 same thing, made to include a larger angle, a greater 

 number of rays are collected, and certain differences 

 appear, and as the angle of vision increases, the 

 structural peculiarities still continue to cause fresh 

 visual phenomena. 



Professor Abbe goes on to say "and cannot be in- 

 terpreted as Morphological but only as Physical 

 characters, not as images of material forms but as 

 signs of material differences in the nature of the 

 particles composing the object, so that nothing more 

 can safely be inferred from the image as presented 

 to the eye, than the presence in the object of such 

 structural peculiarities as will produce the particular 

 diffraction phenomena, on which the images de- 

 pend." 



The wonderful discovery is that the Microscope 



