6 4 



ELEMENTARY PHOTO-MICROGRAPHY. 



appointed time, so being free to do other things 

 meanwhile. 



The conditions governing correct exposure are 

 so varied that no rule can be stated, and the 

 following examples are merely given to point out 

 the probable variations likely to occur in photo- 

 graphing assorted specimens. The distance of the 

 object from the plate was about i8in., the source 

 of illumination a paraffin lamp with a lin. wick. 



A FEW EXAMPLES OF EXPOSURE. 



3in. OBJECTIVE. 



Transmitted 

 Light. 



Dark 

 Ground. 



Reflected 

 Light. 



Polariscope. 



Section of Human Tongue. Red. " A " eyepiece. No con- 

 denser. Chromatic plate. One minute. 



Leg of Fly. Brown. Ground-glass interposed between 

 lamp and object to secure sharpness of hairs and 

 reduce the white diffraction effects. " A " eyepiece. 

 Slow plate. Four minutes. 



Polycystina. Slow plate. Webster condenser. " A " eye- 

 piece. Four minutes. 



White Coralline. No eyepiece. Slow plate. Side reflector. 

 Five minutes. 



Tongue of Whelk. No eyepiece. Chromatic plate. Five 

 minutes. 



ain. OBJECTIVE. 



Transmitted 

 Light. 



Reflected 

 Light. 



Dark 

 Ground. 



Polariscope. 



Beetle's Eye. Section. Slow plate. Three minutes. " A " 

 eyepiece. No condenser. 



Diatoms mounted as opaque objects. Slow plate, 

 minutes. " A " eyepiece. 



Polycystina. Webster condenser, 

 minutes. " A " eyepiece. 



Few 



Brucine. Eyepiece removed, 

 minutes. 



Slow plate. Four 

 Chromatic plate. Eight. 



