466 



Propagation and Intensity of Light. 



No. 53 630 



53 630. 1 : 3. 



53631. 1:5. 



53 633. 1 : 6. 



53 637. 1 = 4. 



53 639. 1 : 8. 



53.630. Aperture Goniometer after Gotschlich, F i g u r e, for the same purpose, giving simul- 8 - d - 

 taneously the upper and central angle of incidence 2.4.0 



The apparatus consists of a stand with graduated arc in the centre of which are two rotary 

 mirrors. The axes of rotation of the mirrors are indicated by engraved lines Two pointers are con- 

 nected with the mirrors and show the predominating inclination on the graduated arc. By means of 

 a spectacle-shaped sighting arrangement with fine ilirends a sight is taken of the mirror, which is 

 adjusted in such manner that the engraved axis of the one mirror falls in a line with the upper edge 

 of the window, while the axis of the other is made to coincide with the ridge of the opposite house. 

 The portion of the arc situated between the two pointers is equal to half tin- angle of aperture. 



53.631. Photometer after \Vingen, Figure, for directly determining the luminosity of 

 workplaces in metric candles (range 10 50 metric candles) 2. 0.0 



The area to be investigated is compared by observing with a red glass with a rotary surface 

 inside the apparatus, this latter surface being illuminated by a small benzene lamp, the height of flame 

 of which can be regulated. By rotating the comparison area relatively to this lamp, an external pointer 

 is actuated, and permits the luminous value of the area investigated to be read off on a scale direct 

 in metric candles. 



53.632. Carrying Case for above, lock-up, with handle 0. 10. 



Cl. 1205,5930, 



59'.>9, 372, 1209. 



