40 ELEMENTARY PHOTO-MICROGRAPHY. 



A small iris diaphragm called a Davis shutter will 

 be found useful for getting better penetration and 

 definition. This screws into the body tube of the 

 microscope at one end, and receives the objective 

 at the other end. It removes any halo or glare, 

 and enables a sharp picture to be taken. For 

 feathers, eggs of insects, and polycystina it is 

 almost indispensable. 



BASEBOARD FOR USE WITH AN ORDINARY 

 MICROSCOPE. 



A carpenter may be got to construct a simple 

 baseboard, on which the lamp, microscope, and 

 camera may be placed. At one end of the board 

 two flanges are fastened, between which a block 

 bearing the camera on the top slides freely to and 

 from the microscope. This sliding block, again, 

 has flanges to receive the small camera and keep it 

 rigidly in position whilst drawing the dark slide. 

 Two thumbscrews in one flange of the baseboard 

 will fix the sliding block, and will secure both 

 block and camera after connection with the micro- 

 scope by means of a velvet tube has been made. 



Note that the bellows of the camera must be 

 capable of full extension when placed in the recess 

 on the top of the block. Thus enlargement may 

 be regulated by racking the bellows in or out 

 without disturbing the connections. A reference 

 to the sketch (fig. 13) will make this clear. 



