192 



Messrs. St. Landau and Ed. Stenz on the 



the nicols the eye looked at a surface o£ paper, which was 

 painted with a colour resembling closely the hue of fluores- 

 cence (p, fig. 2). This screen was illuminated by light, 



Fig. 2. 



-\ 7n 



reflected by a glass mirror, coming from the source, which 

 was a 500 watts incandescent lamp. A little fragment of 



