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NOTE ON STEREO-PHOTO-MICROGRAPHY. 



By Arthur E. Smith. 



(Read May 18th, 1906.) 



Plates 31—33. 

 There are several ways of making stereoscopic slides from micro- 

 scopic objects. The simplest way is by using an excentric 

 " Waterhouse " stop just behind the objective, where there is 

 a short length of additional tube, with a fine slot in one side 

 (Fig. 1). The camera is placed in conjunction with the microscope in 

 the usual way and the object focussed. The excentric stop is then 

 inserted in the slot ; this sharpens up the image, and has the effect 



6 



Fig. 1. 



of " seeing " the image from only one side of the objective. 

 A negative is now taken. The stop is then reversed and another 

 negative taken. The prints from those negatives are distinctly 

 different and make good stereoscopic pairs. A quarter-plate 

 camera will be large enough, as the two images come practically in 

 the same place. This seeing double with a single lens can be 

 more easily illustrated by a view camera than with a microscope. 



Take any view camera with any len>. and put an electric glow- 

 lamp in the camera and focus the filament on a sheet of papi r. 

 The image is single but somewhat blurred. Now put in front of the 

 lens a "two-eyed" stop, as in the illustration, and two very 

 distinct and sharp images w T ill appear, showing that the two >ides 

 of the lens, through the two stops, see the electric filament from 

 different points of view (Fig. 2). If the lamp is outside and 

 focussed on the ground glass the result is the same, but then the 

 images can only be examined by one person at a time. 



A curious variation is to have a piece of card with one hole 



