260 Transactions of the Society. 



V. — A Simple Method of taking Stereo-Photomicrographs, and 

 Mounting the Prints without Cutting. 



By H. Tavern er. 



(Read February 21, 1906.) 

 Plates IX., X. and XI. 



In November 1903 I had the pleasure of exhibiting to the Fellows of 

 this Society two photographs of the hairs on the leg of a water-mite, 

 which I had taken through the right and left tubes of a binocular 

 Microscope, in order to demonstrate that the two images were not 

 identical. I did not bring the matter forward as a new discovery, 

 but simply because the object was particularly suited to demon- 

 strate the fact, which I knew was disputed by some microscopists. 

 The photos in question were too small to be viewed stereoscopic- 

 ally, and I therefore exhibited under a stereoscope at the same 

 time two photos of the same subject, taken by a different method 

 with a magnification of over 200 diameters, which proved that the 

 two dissimilar images combined to form a stereoscopic picture. 

 The method then adopted for the production of the photos was to 

 cover the front of the objective with a cap (fig. 38), by means of 

 which exactly one half of the front of the lens was cut off. The 

 rotation of this cap through 180° allowed separate pictures to be 

 taken by the right and left halves of the lens. 



I did not pursue the matter further at the time ; but shortly 

 before Christmas last I wanted a similar photo for a friend, and it 

 then occurred to me that the axial rays of light were detrimental 

 to the formation of a stereoscopic image, and that if I could stop 

 them out, I should obtain better results stereoscopically than by 

 my former method. I therefore tried the experiment of cutting 

 out all the central rays of light by means of a stop placed behind 

 the objective, having a circular aperture, so situated that its inner 

 edge was outside the optic axis of the lens (fig. 39). The resulting 

 photos were a decided improvement on those obtained by my former 

 method ; and on showing these to Mr. Eheinberg, he confirmed me 

 in my intention of experimenting with stops of smaller aperture. 



I do not think I need say anything further on this point, 



EXPLANATION OP PLATE IX. 



Water-mite (Ecpolus papillosum Soar) female, x 30. Collected and mounted by 

 H. Taverner. Photographed with a 2' 5 mm. stop. Beck's l£-in. objective 

 and No. 1 eye-piece. 



