THE PHOTO-MICROGEAPHIC CAMEEA 117 



work that would be possible with such an apparatus. As this 

 camera is reasonable in price, and substantially made, it is 

 one that may be recommended where an elaborate outfit is 

 not desired. 



Some form of vertical apparatus is, however, an absolute 

 necessity at some time or another to the photo-micrographer, 

 and the type adopted by the writer is that known as Van 

 Heurck's vertical camera, made by Messrs. W. Watson & Sons 

 of High Holborn (Fig. 40). This apparatus is particularly 

 rigid, and, as the illustration shows, consists essentially of an 

 elongated box supported on either side by strong supports, and 

 carrying the focussing-screen and dark-slide at its upper end. 

 On the side of the box near to the observer is a door which, while 

 it can be opened for making any adjustment to the microscope, 

 is perfectly light-tight when closed and ready for taking a photo- 

 graph. The chief objection to its use is that there is no method 

 of altering the distance between the microscope and the focussing- 

 screen, so that any variation of magnification has to be entirely 

 effected by a suitable combination of objective and ocular. In 

 practical work, however, this is a comparatively small matter 

 and one that a little ingenuity will overcome. The apparatus is 

 very convenient for photographing objects that may lie in 

 fluid, or in cases where for any other reason the microscope 

 cannot be inclined. 



The dark-ground illumination methods that have lately been 

 re-introduced have rendered the photographing of such objects 

 as living bacteria quite within the bounds of ordinary work, 

 and the apparatus is eminently suited for this purpose. 

 The table on which the microscope is supported should be 

 very strong and stiff, and it is essential to see that when the 

 camera is placed over the microscope it is perfectly steady 

 and is standing on a level surface. The apparatus as shown 

 is supported on four points, and mechanically this is unsound. 

 The writer's modified apparatus is made with one strong leg 

 on either side, and a third one on the opposite side to that 

 on which the observation-door opens. The worker is therefore 

 independent of any inequalities of either table or bench, as 

 the apparatus, being supported on three points, will in any 

 case stand quite firmly, while being as stable as when 

 supported on four points. 



