ELEMENTARY PHOTO-MICROGRAPHY. 23 



is, of course, much more brilliant without the eye- 

 piece, reducing exposure considerably, yet the 

 defect in uniformity of illumination would spoil the 

 negative. On replacing the eyepiece the bright 

 spot of light vanishes, and the whole disc is equally 

 lighted, though not so brightly as before. 



First attempts should be made with well-defined 

 objects possessing contrast, such as the section of 

 a stem, rather than with those that are very trans- 

 parent all over. 



