ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



143 



which is supported over the Microscope by the pillars, A. A tube 

 inserted in an opening in B forms the connection with the Microscope, 

 and the camera can be brought by a sliding arrangement into six 

 different positions, corresponding with the photographic plate. D is 

 the illuminating apparatus, consisting of mirror, condensing lens, and 

 movable screen to shut off the light as required. 



Apparatus for taking Stereoscopic Photo-Micrographs. — Stereo- 

 scopic photo-micrographs could of course be obtained by applying a 

 camera to each end of the tubes of a binocular Microscope, and taking 

 two photographs simultaneously, or as suggested by Babo, by slightly 

 raising either end of the slide alternately, or again by taking a second 

 photograph with the objective focused to a lower plane of the object 

 than that to which it was focused when the first was taken. A 

 combination of these two methods is said by Dr. S. T. Stein * to give 

 excellent effects. 



Dr. A. Moitessier suggested f the apparatus, fig. 33. The fixed 

 tube A, attached to the body-tube, has a second ex- 

 ternal tube B, which rotates upon it, a pin working 

 in a semicircular slot D stopping the rotation beyond 

 180^. At the end of B is attached a half-dia- 

 phragm C, and the objective is screwed over the 

 diaphragm. On rotating the tube in opposite 

 directions, the diaphragm takes the positions E and 

 E', so that opposite halves of the objective are 

 alternately made use of and different images ob- 

 tained. Photo-micrographs thus taken will give 

 stereoscopic or pseudoscopic effect, according as 

 they are mounted, The apparatus will only act 

 effectively with low powers and opaque, not trans- 

 parent, objects. 



In order to alter readily the inclination of the 

 object to the axis of the Microscope, Dr. B. BeneckeJ devised the 

 apparatus shown in figs. 34 and 35. 



A circular plate A, fig. 34, with a central opening, is fixed by the 



Fig. 33. 



tube F in the aperture of the stage. The vertical pieces E support a 

 similar plate B G, which swings on a horizontal axis passing through 



* ' Das Licht im Dienste Wiss. Forschung,' 1884, p. 197. 

 t ' La Photographie appliquee aux recherches micrographiques,' 1866, p. 148. 

 X ' Die Photographie als Hiilfsmittel Mikroskopischer Forschung,' 1868, p. 81 

 (2 figs.). 



