ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



229 



Kniss Epidiascope.* — This instrument, which was described in 

 this Journal,! ant ^ was invented rather more than a year ago, has lately 

 been improved in certain details and adapted by A. Kriiss to a greater 

 range of purposes. Figs. 57 and 58 of the former abstract illustrate 

 the principle, while the accompanying figs., 23, 24, show the new applica- 

 tions. Fig. 23 shows the epidiascope in normal adjustment. A self- 

 regulating lamp for 30-50 amperes acts as the light-source. Transition 

 from diascopic to epidiascopic projection is effected by pressure on one of 



Fig. 24. 



the levers seen in the figure. If both mirrors (S t S 4 original fig. 57) are 

 thus put out of action and the front wall let down (fig. 24), the light- 

 rays may then pass axially through the apparatus, and an optical bench 

 may be inserted. Fig. 24 also shows the optical bench adapted for polarisa- 

 tion demonstrations. Suitable arrangements may be similarly made for 

 exhibition of spectral, interference, and diffractive phenomena. A pro- 

 jection Microscope can be applied to the bench. Sometimes this Micro- 

 scope objective would be equally suitable for the projection of opaque 

 objects or of diapositives. But when considerable magnification is re- 

 quired, and increased distance from the screen is unattainable, the 



* Deutsch Mech.-Zeit., 1909, pp. 230-2(3 figs.). 

 t See this Journal, 1909 p. 251. 



