304 PRACTICAL PHOTO-MICROGRAPHY 



PLATE X, FIG. 2.- Metal Surface Silver and Copper Alloy. 

 X 250. 



Objective, J-inch achromatic, by James Swift & Son 

 (corrected for uncovered objects). Tube-length, 220 mm. 



Zeiss projection-ocular, 2. 



Illuminant, quartz mercury-vapour lamp, taking 2-5 

 amperes at 240 volts. 



Zeiss vertical illuminator. Plano-convex lens interposed 

 between the source of light and the illuminator, throwing a 

 convergent beam into the reflecting prism of the latter. 



Critical image of the illuminant projected on to the metal 

 surface. 



Screen, filter-yellow-K. 



Wellington orthochromatic process plate. 



Exposure, 20 seconds. 



Development by pyro-soda. 



PLATE X, FIG. 3. Cemented Steel, showing Carbide of 

 Iron. X 100. (Negative by C. 0. Bannister, Esq.) 

 Objective, 16-mm. apochromat, by Carl Zeiss. 

 Projection-ocular, No. 2. 

 Zeiss vertical illuminator. 

 Ordinary blue-green glass screen. 

 Camera-length, 80 centimetres. 

 Illuminant, electric arc, 20 amperes. 

 Plate, Barnet medium orthochromatic. 

 Exposure, 16 seconds. 



PLATE X, FIG. 4. Metal Surface Manganese Sulphide in 

 Steel. X 1000. (Negative by C. 0. Bannister, Esq.) 



Objective, 2-mm. apochromat; oil-immersion, N.A. 1.30. 



Projection-ocular, 2. 



Camera-length, 100 centimetres. 



Blue-green glass screen. 



Illuminant, electric arc, 20 amperes. 



Exposure, 20 seconds. 



