ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



141 



In the box slide four carriers D, for the sensitive plates, and these 

 can bo placed in position over the central opening one after another 

 and a negative taken.* The special advantage of the apparatus 

 is that it enables different degrees of exposure to be tested, or 

 different portions of an object to be rapidly photographed in 

 succession. 



A simpler form of camera is shown in fig. 29, on the same principle 

 as the preceding, but for one plate only. 



Fig. 29. 



For focusing it is necessary first to regulate the focusing lens F, 

 which is a single lens in an adjustable screw mounting. For this 

 purpose a square of glass is placed in the box C, on the lower face of 

 which some scales have been fastened. The lens is then placed so 

 that the base-plate is applied exactly to the upper edge E of the box 

 C. It is then focused on the scales by screwing the lens in or out, 

 and is then clamped by the set-screw. The lens, when thus regulated, 

 will of course only serve for the particular person to whose sight it 

 has been adjusted. 



The sensitive plate is placed in the carrier D, and its contact with 

 the guides on the bottom of the box assured by turning the screw I 

 gently. The image of the object is then focused by the adjustments 

 of the Microscope, again applying the lens F upon E and using it 

 as an eye-piece. 



Dr. B. Benecke f devised the camera, fig. 30, for taking eight 

 photo-micrographs. In a circular camera B, rotates a disc A having 

 a square aperture 12 cm. wide in the centre. The bottom of the 

 camera has an opening at C, 2 cm. in diameter, communicating with a 

 tube which fits into the body-tube of the Microscope ; it can be closed 

 by a slider, the handle at which is at D. A plate H, for eight photo- 

 graphs, fits into the aperture in the disc, and can be rotated over C, 

 a spring clip F indicating the eight equidistant positions. The 

 shutter E of the camera is secured by the three catches G, and on the 

 under side it has a spring which presses on the back of the plate. 

 In order to mark the corresponding positions of the different photo- 



* The drawing has been reduced in width. The box of the original apparatus 

 is about a fifth wider so as to leave more space for tlie carriers. 



t 'Die Photographie als Hulfsmittel Mikroskopischer Forschung,' 1868, 

 pp. 54-6 (1 fig.). 



