ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



663 



the camera was focused, the observer's head being thus in close proximity 

 to the Microscope. (A and B are intended to show the mode of illuminating 

 an object by oblique transmitted, and by reflected light.) 



Fig. 1S8. 



Dr. S. T. Stein* adopts the following method of focusing. The Micro- 

 scope A (fig. 189) is first adjusted by direct vision until a clear image of 

 the object is obtained ; the eye-piece m is then removed and the body-tube 

 united with the wooden chamber H by means of the black cloth connection 

 B, which has rubber collars at m and n, and admits no light ; the rays 

 from the mirror / throw a blurred image of the object upon the ground- 



FiQ. 189. 



glass plate of the camera C. Behind the camera is the plane mirror D, in 

 which the observer whose eye is near the Microscope sees this image ; he 

 is thus in a position to adjust the Microscope until a well-defined image i - 

 thrown upon C by the direct use of the micrometer-screw r without the 



• Stein, S. T., 'Das Licht,' 8vp, Halle, 1884, pp 231-2 (1 fig.). Cf. also J. Girard's 

 • La Chambre noire et la Microscope,' 2nd ed,, 1870, pp. .'i2-?> (1 fig.). 



