34 ELEMENTARY PHOTO-MICROGRAPHY. 



illumination of the field, we are ready for the 

 exposure. At present we need not be concerned 

 about the amount of magnification. 



A cap placed on the lens, or a piece of black 

 cardboard reared in front of it, will exclude light 

 from the camera while the shutter of dark slide is 

 withdrawn, if precaution be taken first to lower all 

 the lights in the room except the lamp. 



When everything is in readiness, remove the 

 cap, or cardboard, and expose for as many seconds 

 or minutes as may be necessary, for which informa- 

 tion read the chapter on exposure. Again cap the 

 lens, or replace the cardboard, and close the dark 

 slide, and the plate is ready for development. 

 Slow plates of almost any brand will do for a start. 



If any difficulty be experienced in getting even 

 lighting over a large field, it may be instantly over- 

 come by using a lantern instead of the oil lamp and 

 bull's-eye ; first removing the projection lenses, 

 and leaving only the large inner condenser for 

 illumination purposes. 



REFLECTED LIGHT FOR OPAQUE OBJECTS. 



With a transparent object like that last de- 

 scribed, it will be remembered the light was sent 

 through it from the back, but when the object is 

 opaque this cannot be done, consequently another 

 method is adopted, viz., lighting from the front 

 instead of the back. 



