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M MMAKV oC CURRENT RESEARCHES RELATING TO 



Fig. 22. 



made of two equal-sized plates united by a hinge. The upper plate 

 forms the base of the camera, which is pyramidal in shape ; the lower 

 is provided with a brass tube, accurately centered, by which the camera 

 is adapted to the tube. If tho preliminary adjustment is made by 

 means of rackwork, the brass tube may be an elastic cap which is fixed 

 to the upper part of the Microscope by a screw clamp. To secure 

 greater stability, it is better to apply this camera to a stand, with which 

 the preliminary focusing is made by a sliding movement. In this case 

 the use is recommended of a strong brass tube of the same size as the 

 body-tube, ending in a screw-thread similar to that of the objectives. If 



it is desired to use objectives of 

 different screw-threads, it will be 

 better to employ several brass 

 tubes of 8 cm. length, which can 

 slide into the tube fixed at the 

 centre of the lower plate. This 

 camera will be especially useful 

 in obtaining plates which give 

 the full views so useful as aids 

 towards drawing. As the ampli- 

 fication will never be more than 

 200 times, cardboard holders will 

 be quite sufficient. The size of 

 the plates is 6 cm. by 6 ■ 5 cm., and 

 they are made by cutting a plate 

 of 13 cm. by 18 cm. into six parts. 

 The slide for the transparent 

 glass is made of cardboard ; the 

 glass is covered with a fine net- 

 work of lines. The hinge which 

 unites the two basal plates enables 

 the camera to be lowered beside 

 the Microscope. This arrange- 

 ment is very useful when the 

 apochromatic objectives of Zeiss 

 are used, and also with the pro- 

 jection eye-pieces constructed for 

 photomicrography. The eye- 

 pieces can then be easily changed. 

 This arrangement was formerly 

 less necessary than now, for with 

 the objectives then used, photo- 

 graphs were almost always taken 

 without the eye-piece. 



The second camera (fig. 22) 

 is sufficient for all the purposes of 

 photomicrography. It is similar 

 to that of Nachet, from which it is only distinguished by the bellows, by 

 a slide in the basal plate, and by a levelling apparatus formed of a plate 

 of zinc upon three screws. 



This camera can be used in the horizontal (fig. 23) as well as in the 

 vertical position. In the former it draws out to 90 cm. ; in the latter 

 to 50 cm. The transparent glass is made as in the preceding camera. 



