764 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in the top facilitates adjustment and transmission of the image. The 

 reflector is made in two sizes, whose diameters are 30 mm. and 50 mm. 

 Exactly similar reflectors are also made out of metal. 



^ '\ReKechr 



i M I I 



-^ ' ' -k Oojecltltes 



Fig. lt>9. 



The same firm also supply round object-slides of white mirror-glass, 

 with a metal plate cemented on to the centre ; the effect is to give a 

 completely black underground. 



(4) Photomicrography. 



Photography by Natural Lenses.* — W. F. Watson has used the 

 crystalline lens from a bullock's eye for photography. A lens-holder 

 was constructed out of a small cardboard pill-box, with a perforated 

 ledge inside for the reception of the eye. The lid and floor of the box 

 are pierced with circular holes smaller than the lens, and it was found 

 necessary to keep its surface moistened with a brush. The lens must 

 be so placed that the flatter surface is underneath and the rounder one 

 uppermost ; and, when once arranged, it must, if possible, not be 

 touched, owing to its delicate nature. The object to be photographed 

 was illuminated with natural light in the ordinary way. It was found 

 an improvement to enclose the crystalline lens, fresh from the animal's 

 eye, between two large watch-glasses of suitable curvature and true 

 shape, their inner surfaces being moistened. These lenses were then 

 completely covered with blackened gummed paper, with the exception 

 of the small circular openings in the middle of the convex surfaces. 

 The lens so prepared could then be applied to the camera. 



The author has also used the eye-lens of a fly for photographic pur- 

 poses, and has reproduced the well-known multiple images. He gives 

 specimens of his success. 



Marktanneb-Tukneretscheb, G. — Wichtigere Forschritte auf dem Gebiete 

 der Mikrophotographie und des projektionswesens. 



[Gives a comprehensive re'sume of international progress in these depart- 

 ments of science.] S.A. Jahrb. /. PhotograpMe und Eeproduhtions- 



technihf., Halle, 1903, 10 pp. 



» Scientific American, quoted in Central-Zeit. f. Opt. und Mech., xxiv. (1903) 

 pp. 144-6 (7 figs.). 



