L9 



II. — A Simple Method of Obtaining Instantaneous 



Photomicrograph s. 



By J. Edwin Barnard. 



(Read November 16, 1910.) 



In view of the considerable development, or what perhaps might 

 more properly be described as the re-introduction of dark-ground 

 illumination methods, it is desirable that some simple method 

 should be available for photograph- 

 ing living or moving microscopic 

 objects. 



Various arrangements have 

 already been described for effecting 

 this, but they are of necessity some- 

 what elaborate and costly. The 

 method that I have recently em- 

 ployed is to use an ordinary reflex 

 camera in conjunction with a vertical 

 photomicrographic camera. It may 

 be that this is a perfectly well-known 

 arrangement, but, if so, I can only 

 say I have not hitherto seen any 

 description of it. 



The type of vertical camera most 

 suitable is that usually known as the 

 Van Heurck model, as made by 

 Messrs. Watson, for this camera is 

 much more stable and stiffly sup- 

 ported, not relying for its stability 

 on a single rod as do most other 

 vertical types. The lens, and if 

 possible the whole front, is removed 

 from the reflex camera, and it is 

 then placed face downwards on the 

 top of the vertical photomicro - 

 graphic camera. The focusing screen 

 is vertical and faces towards the 

 observer. It is then quite easy to observe the image on the 

 ground-glass screen of the reflex camera through the focusing 

 hood, and at the same time to control with ease the necessary 

 adjustments of the Microscope. Exposure would, of course, be 



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Fig. 1. 



