30 ELEMENTARY PHOTO-MICROGRAPHY. 



Commencing with a simple object and the lowest 

 power, we first set up the baseboard, with lamp, 

 microscope, and camera duly placed in position (see 

 fig. 9), but as an object may be photographed either 

 by direct transmitted light, reflected light, and with 

 dark ground or light ground, we will consider trans- 

 mitted light and a light background first. 



Having placed the object on the stage of the 

 microscope, it is focussed with the A eyepiece, the 

 camera and sliding block haying been removed 

 for this purpose. No substage condenser is needed 

 for powers lower than lin. ; therefore the critical 

 light to be used for high powers may be replaced by 

 the ordinary parallel rays from the bull's eye after 

 the paraffin lamp has been set according to> the in- 

 structions previously given. The eyepiece is next 

 taken out and a piece of white cardboard placed 

 about i2in. away from the end of the body tube to 

 act as the screen, and receive a, projected image from 

 the microscope. The disc of light will possibly be 

 found brighter in one part than, another. The 

 lamp is moved sideways until the whole disc is 

 equally illuminated with the object well defined in 

 the centre. The focussing may be altered for this 

 purpose. The eyepiece is replaced to< see if the 

 field be still uniformly lighted, a slight adjustment 

 of focus again being necessary. If the lamp be in 

 the right position the disc of light will be sharp and 

 uniform right up to the edge of the circle with or 

 without an eyepiece. The cardboard is taken away, 

 and the camera brought up to 1 the microscope with 



