PHOTO-MICROGRAPHY BY MAGNESIUM LIGHT. 2IQ 



advantages. For this process a good lamp is necessary, 

 and the one shown in Fig. 198 is the best of its kind. 



In describing the magnesium modification of photo- 

 graphy as applied to the amplification of microscopic 

 objects, Colonel Woodward compares the light given off 

 by a good magnesium lamp to white-cloud illumination of 

 the best character. 



Without the use of ground glass, this light serves ad- 

 mirably for the production of photographs of soft tissue 

 with any power under 1000 diameters. The light being 

 composed of a mixed pencil, with rays passing in all 

 directions, there are no interference phenomena ; but for 

 the same reason, on the Nobert's plate and many test- 

 objects, the results are inferior to those produced by the 

 sun or by the electric light ; with powers much higher than 

 1000 diameters, however, the time of exposure becomes 

 inconveniently long. 



FIG. 199. 



The condenser concentrates the light on the lower lens of 

 the achromatic condenser of the microscope as shown in 

 Fig. 199, which stands on a table supported by three 

 levelling screws. The image is received on the plate- 

 holder supported on the table, and photographed precisely 



