142 PRACTICAL PHOTO-MICROGRAPHY. 



ary negative gelatine plate, for making an enlarged negative, 

 the greatest care must be taken to prevent extraneous light 

 reaching the sensitive plate. If a lantern of the ordinary type 

 is used it should be enclosed in a box, the lens only protruding 

 through a fitting aperture. 



In enlarging, beautiful effects may be produced very simply 

 by judicious " vignetting " ; an opaque mask having a suitably 

 sized and shaped aperture cut in it may be moved towards and 

 from the sensitive material during the exposure. Such matters 

 are treated in most books devoted to photography. 



