78 



Franz Schmidt & Haensch, Berlin S. 



cannot or can only with great inconvenience be used. The instrument is 

 indispensable for examining the light admitted into school rooms etc. 



Fig. 15. 



Detailed description and directions for use may be had of the" 

 firm's representative. 



II. L. Weber's Apparatus for measuring solid angles (Fig. 16). 



,P 



Fig. 16. 



For measuring the solid angle contained by the incident rays and 

 the illuminated surface. (For further particulars vid. Description alluded 

 to above.) 



