ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



87 



tins a camera with considerable bellows extension is necessary, and the 

 lens must be midway between tbe object and the camera glass. The best 

 work will be possible with a wide-angle lens of rather short focil length. 



Fig. S. 



Extreme care and cleanliness arc urged ; dust is a great enemy in full- 

 size photography. It will generally be found necessary to arrange a 

 wire frame with velvet hood to cover the camera top so as to exclude 

 all reflections. 



Penny, It. Greenwood — Photomicrographic Apparatus. 



Amer. Mm. Mirr. Jonrn., Nov. 1890, pp. 310-4; 

 and English Mechanic and World of Science (reference not given) 



(5) Microscopical Optics and Manipulation. 



Imitation of Polarised Light Effects by Diffraction.* — Mr. J. 

 Eheinberg, by inserting a straight-lined diffraction grating of 100 lines 

 per millimetre (about 2500 per inch) just above the objective, and focus- 

 sing down on a small piece of wire gauze (wires 0*5 mm. apart), produces 

 a series of brilliantly coloured results, which are strongly suggestive of 

 polarised light effects ; although, in reality, they are diffraction fringes. 



* Joura. Quek. Micr. Club, 1900, pp. 407-10 (2 figs.). 



