ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



705 



scope by slightly racking back the condenser. The image of the saw- 

 teeth constitutes the measuring scale which can be given any desired 

 value, within limits, by adjusting its distance from the Microscope 

 mirror and comparing the focussed image with the scale on a stage 

 micrometer. When the scale is nob wanted the block is pushed aside 

 and can be replaced in an instant. An engraved scale on glass, or 

 celluloid, could be substitute 1 for the saw.* 



Fig. 134. 



Form of Vertical Camera and its Uses.f — J. Reighard has ar- 

 ranged an apparatus for photographing such objects as the eggs of 

 Amia, which are some 2 mm. in diameter, spherical and opaque, and 

 must be photographed under liquid with a vertical camera. He used 

 Zeiss' larger photomicrographic camera, which is made in two sections 

 so that the front section alone may be employed where a short bellows 

 is desired. The camera was attached by means of clamps to an iron 

 frame consisting of two iron rods held together by cross bars at the 

 ends and middle, and the length of the bellows could be varied by the 

 adjustment of the clamps. The frame could be slid backwards and for- 

 wards in four grooved supports screwed to the top of an iron stand : 

 this top was a heavy I-shaped casting bolted to the rest of the stand. 

 A fine adjustment was secured by the following device : — Alongside 

 the camera frame (on the left) at a distance of 5 cm. from it runs a 

 vertical wooden rod 3 to 4 cm. in diameter (fig. 135) ; this rod is 

 pivoted at its upper end to the ceiling near the first pulley wheel, and 

 at its lower end it is pivoted on a wooden bracket which extends from 

 the wall just below the board to which the iron base-plate is attached ; 

 the rod is thus within easy reach of a person focussing the camera, and 

 turns freely ; its upper end for about 6 cm. is formed into a spool and 



* This is a variant of the ghost micrometer described by Dr. Goring in ' Micro- 

 graphia,' 1837, p. 51. It has since been re-invcnted manv times, 

 t Journ. App. Micr., v. (1902) pp. 1782-90 (7 figs.). 



December 17th, 1902 3 b 



