698 



siMMARY OF CURRENT RESEARCHES RELATING TO 



ray is a continuation of that of the incident ray. The author also dis- 

 cu^srs some otjier forms of prisms suitable for the same purpose. 



E Go 



a I 

 I 



I / 



A i iff, B 



: i 



xT?L _ _ 



Fig. 82. 



Fig. 83. 



Aids to Crystalloptic Projection.* — In discussing the above subject 

 J. Beckenkanip recommends the use of a lantern-screen prepared with 

 aluminium bronze. Photometric tests of such a screen in comparison 

 with screens of other kinds are very much in its favour. The most 

 advantageous position is to arrange so that the incident beam of light 

 falls horizontally on the vertical screen ; moreover, the light-beam should 

 be central with regard to the auditorium, the screen being about 3-4 m. 

 from the lantern. The spectators should be ranked on each side of the 

 optic axis of the lantern, and, if possible, the rows should rise in tiers 

 one behind another. 



Emrys-Roberts Microscope Lamp. — This apparatus (fig. 84) was 

 exhibited and described at the June Meeting (see Proceedings, ante, 

 p. 571). 



Fig. 84. 



Model of the Vibration-planes of Light in the Polarizing Appa- 

 ratus, t — In order to assist the realization of the path of a ray of light 



* SB. Pliys. Med. Gesell. zu Wiirzburg, 1911, pp. 13-16. 

 t Zeitschr. wiss. Mikrosk., xxviii. (1911) pp. 42-5 (1 fig.). 



