THE PHOTO-MICBOGBAPHIC CAMERA 141 



mirror and effecting the exposure ; also that the period elapsing 

 between the release of the mirror and the actual exposure 

 of the plate should be as short as possible, so that if any 

 vibration is started, it will not have time to be transmitted 

 to the rest of the apparatus. 



An elaboration of the same idea and an arrangement suit- 

 able for use in conjunction with a large horizontal apparatus, 

 such as that made by Zeiss already described, has recently 

 appeared. 1 It consists essentially of a reflex camera of special 

 design which is placed in a position between the microscope 

 and the focussing- screen of the camera, occupying, in fact, the 

 place usually taken by the conical front of the camera. The 

 image is viewed in a position above that where connection is 

 made between the microscope and the camera, so that double 

 reflection of the image takes place between two mirrors placed 

 in a suitable position inside the reflex portion. It was designed 

 for the same object as the vertical apparatus just described, 

 but it appears to be open to the objection that it is not available 

 for the photography of objects in fluid, and in which therefore 

 the microscope must remain in a vertical position. In other 

 respects it would no doubt fulfil its purpose perfectly. Its chief 

 advantage appears to be that the operator is able with ease to 

 adjust both the coarse- and fine- adjustment focussing- screws of 

 the microscope ; and also at will to effect any movement of 

 the stage or alteration of the sub-stage illuminating apparatus, 

 while at the same time being able to see the result of any 

 alteration of these adjustments on the ground-glass screen. 



For metallurgical work, or the systematic photographing of 

 opaque objects, an arrangement must be made for supporting 

 the source of light at right angles to the optical axis, so that 

 a vertical illuminator or any other arrangement for opaque 

 illumination may be used. This can be simply arranged by 

 having a support on either or both sides of the base carrying 

 the camera, or on any table or bench that is carrying the 

 apparatus. It is convenient, however, in any case to arrange 

 that the illuminant is so supported that it is possible to alter 

 the distance between it and the illuminating apparatus while 

 keeping it in perfect alignment. 



When using the auxiliary illuminating appliances that are 



1 British Journal of Photography, March 12, 1909, p. 193. 



