74 



THE MICROSCOPE 



Vertical 

 photo- 

 micro- 

 graphio 



camera. 



tte stage of tte instrument, and tlie slide of the plate-holder 

 is drawn. The exposure may now be made by withdrawing the 

 card, replacing it and closing the plate-holder. 



The use of colour screens (see page 42) is of great service in_ 

 photography to increase contrasts, but the student is referred 

 to books on this subject for detailed information as to photo- 

 graphing difficult objects. 



At the same time, the photography of most microscopic 



objects is so simple that 

 the ordinary observer 

 need not be deterred by 

 the complexity of the 

 instruction given for the 

 most advanced work. 



There are two general 

 forms of photomicro- 

 graphic cameras. One is 

 vertical and is used with 

 the microscope in a ver- 

 tical position. The other 

 requires the microscope 

 to be placed in a hori- 

 zontal position, and con- 

 sists of a metal bar 

 on raising and lowering 

 screws which carries a 

 camera with a variable 

 extension adjusted by 

 means of bellows. 



The vertical camera 

 consists of a frame stand- 

 ing on three strong legs 

 splayed out to give sta- 

 bility. It has a slide 

 FiQ. 86. — No. 3342, Vertical Photomioro- on its upper surface into 

 graphic Camera. which either a ground 



glass screen or a double 

 plate-holder is inserted. Below this frame is a flexible bag 

 which fits over the upper end of the drawtube of the microscope 

 and can be attached by a cord. The size of plate used is 4J X 3J- 

 inches (quarter-plate), and the distance from the upper end of 

 the standard microscope is such that, with the 30-mm. compen- 

 sating eyepiece, it gives a circular picture of about 3 inches. It 

 is rigid, and Ught, and extremely convenient. When the micro- 

 scope is adjusted with all the care required to obtain the best 

 image the camera is placed over it, attached to the tube by means 

 of the bag, and a touch of the fine adjustment is aU that is neces- 

 sary. In order to focus the imageon the ground glass accurately, 



